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矢口 裕之 ヤグチ ヒロユキ

所属部署名 理工学研究科 数理電子情報部門 電話番号
職名 教授 ■FAX番号
住所 埼玉県さいたま市桜区下大久保255 ■メールアドレス yaguchi@opt.ees.saitama-u.ac.jp
■ホームページURL http://www.opt.ees.saitama-u.ac.jp/

プロフィール

兼担研究科・学部

工学部 電気電子システム工学科

研究分野

応用物性・結晶工学
物性I
電子・電気材料工学
キーワード:光物性 , 光エレクトロニクス , 分子線エピタキシー , エピタキシャル成長 , 光エレクトロニクスデバイス

現在の研究課題

半導体薄膜結晶成長および光物性評価
分子線エピタキシーや有機金属気相成長によって作製した歪ヘテロ構造におけるバンド不連続量についてフォトリフレクタンス法を用いて研究を行った(Phys. Rev. B49, 1994)。GaP1-XNX混晶について,バンド端形成が他の混晶系とは全く異なっていることや,発光がバンド端よりも低いエネルギーの空間的に局在した準位で起こっていることなどを明らかにした(J. Crystal Growth 170, 1996)。さらにバンド端形成機構の理論的検討を行った(J. Crystal Growth 189/190, 500, 1998)。現在,短波長発光デバイス材料として期待される窒化物半導体に関する研究を進めている。
光通信用半導体レーザの材料として期待されるIII-V-N混晶半導体に関する研究
パワーデバイス応用のためのSiC/酸化膜界面に関する研究
InNのMBE成長および物性に関する研究
等電子トラップによる単一光子発生に関する研究

所属学会

所属学会
応用物理学会
American Physical Society
Materials Research Society
日本光学会

学歴

出身大学院・研究科等
1991 , 東京大学 , 博士 , 工学系研究科 , 物理工学専攻 , 単位取得満期退学
1988 , 東京大学 , 修士 , 工学系研究科 , 物理工学専攻 , 修了
出身学校・専攻等(大学院を除く)
1986 , 東京大学 , 工学部 , 物理工学科 , 卒業
取得学位
博士(工学) , 東京大学 , 光変調反射分光法による半導体歪ヘテロ構造に関する研究
工学修士 , 東京大学 , RHEEDによるPb/Si(111)表面超構造の研究
学士 , 東京大学

受賞学術賞

2013 , APEX/JJAP編集貢献賞
1997 , 応用物理学会講演奨励賞
1995 , 井上研究奨励賞

研究職歴等

研究職歴
2009 , 埼玉大学大学院理工学研究科教授
2006 - 2009 , 埼玉大学大学院理工学研究科助教授
1998 - 2006 , 埼玉大学工学部助教授
1991 - 1998 , 東京大学工学部助手

研究活動業績

研究業績(著書・発表論文等)

著書
電気数学
実教出版 2008
ISBN:ISBN 978-4-40-731317-8
吉田貞史, 菊池昭彦, 松田七美男, 矢口裕之, 明連広昭, 石谷善博, 金原粲

基礎物理2
実教出版 200610
ISBN:ISBN 978-4-40-730855-6
金原粲、吉田貞史、江馬一弘、馬場茂、矢口裕之、和田直久

Handbook of Semiconductor Nanostructures and Nanodevices (Optical Gain of Variously Strained Semiconductor Quantum Wells)
American Scientific Publishers, Los Angeles :457-485 2005
ISBN:ISBN 978-1-58-883073-9
Y. Seko and H. Yaguchi

III-Nitride Semiconductors: Optical Properties II (Chapter 9 Cubic Phase GaN and AlGaN: Epitaxial Growth and Optical Properties)
Taylor & Francis Books, Inc. :363-407 2002
ISBN:ISBN 978-1-56032-973-2
J. Wu, H. Yaguchi, and K. Onabe

理工学のための線形代数
培風館
長澤壮之、江頭信二、榎本裕子、古城知己、鈴木輝一、矢口裕之、柳瀬郁夫

Properties and Applications of Silicon Carbide
InTech:77-87
Y. Hijikata, H. Yaguchi and S. Yoshida

薄膜の評価技術ハンドブック
テクノシステム:114-116, 314-138
矢口裕之

Physics and Technology of Silicon Carbide Devices, Chapter 7
InTech:181-206
Y. Hijikata, S. Yagi, H. Yaguchi and S. Yoshida

Nondestructive and Contactless Characterization Method for Spatial Mapping of the Thickness and Electrical Properties in Homo-Epitaxially Grown SiC Epilayers Using Infrared Reflectance Spectroscopy
InTech:3-26
S. Yoshida, Y. Hijikata, and H. Yaguchi

論文
Si emission into the oxide layer during oxidation of silicon carbide
,Materials Science Forum,Vols. 778-780:553-556 2014
Y. Hijikata, Y. Akasaka, S. Yagi, and H. Yaguchi

Enhanced optical absorption due to E+-related band transition in GaAs:N δ-doped superlattices
,Applied Physics Express,7(10):102301 2014
S. Yagi, S. Noguchi, Y. Hijikata, S. Kuboya, K. Onabe, Y. Okada, and H. Yaguchi

Photoreflectance study of the temperature dependence of excitonic transitions in dilute GaAsN alloys
,Physica Status Solidi A, 211(4):752-755 2014
W. Okubo, S. Yagi, Y. Hijikata, K. Onabe, and H. Yaguchi

First-principles study on the conduction band electron states of GaAsN alloys
,Physica Status Solidi C,11(3-4):911-913 2014
K. Sakamoto and H. Yaguchi

Stacked structure of self-organized cubic InN nano-dots grown by molecular beam epitaxy
,Physica Status Solidi C,10 (11):1545-1548 2013
S. Yagi, J. Suzuki, M. Orihara, Y. Hijikata, and H. Yaguchi

Conversion Efficiency of Intermediate Band Solar Cells with GaAs:N δ-Doped Superlattices
,Japanese Journal of Applied Physics,52 (10):102302 2013
S. Yagi, S. Noguchi, Y. Hijikata, S. Kuboya, K. Onabe, and H. Yaguchi

Analysis of Electronic Structures of Nitrogen δ-Doped GaAs Superlattices for High Efficiency Intermediate Band Solar Cells
,IEEE Journal of Photovoltaics,3(4):1287-1291 2013
S. Noguchi, S. Yagi, D. Sato, Y. Hijikata, K. Onabe, S. Kuboya, H. Yaguchi

Direct Evidence of Carrier Excitation from Intermediate Band States in GaPN by Two-Wavelength Excited Photoluminescence
,Applied Physics Express,6(9):092401 2013
A. Z. M. Touhidul Islam, T. Hanaoka, K. Onabe, S. Yagi, N. Kamata, and H. Yaguchi

RF-MBE growth of cubic AlN on MgO (001) substrates via 2-step c-GaN buffer layer
,Journal of Crystal Growth,378:307-309 2013
M. Kakuda, S. Morikawa, S. Kuboya, R. Katayama, H. Yaguchi, K. Onabe

RF-MBE growth of cubic InN nano-scale dots on cubic GaN
,Journal of Crystal Growth,378:454-458 2013
J. Suzuki, M. Orihara, S. Yagi, Y. Hijikata, H. Yaguchi

Molecular beam epitaxy of ErGaAs alloys on GaAs (001)
,Journal of Crystal Growth,378:85-87 2013
R. G. Jin, S. Yagi, Y. Hijikata, S. Kuobya, K. Onabe, R. Katayama, H. Yaguchi

Observation of optical spin injection into Ge-based structures at room temperature
,Applied Physics Letters,102(24):242104 2013
Y. Yasutake, S. Hayashi, H. Yaguchi, and S. Fukatsu

Optical Properties and Carrier Dynamics in Asymmetric Coupled InGaN Multiple Quantum Wells
,Functional Materials Letters,06(2):1350021 2013
G. E. Weng, B. P. Zhang, M. M. Liang, X. Q. Lv, J. Y. Zhang, L. Y. Ying, Z. R. Qiu, H. Yaguchi, S. Kuboya, K. Onabe, S. Q. Chen, H. Akiyama

Biexciton emission from single isoelectronic traps formed by nitrogen-nitrogen pairs in GaAs
,AIP Conference Prodeedings,1566:538-539 2013
K. Takamiya, T. Fukushima, S. Yagi, Y. Hijikata, T. Mochizuki, M. Yoshita, H. Akiyama, S. Kuboya, K. Onabe, R. Katayama and H. Yaguchi

Biexciton Luminescence from Individual Isoelectronic Traps in Nitrogen delta-Doped GaAs
,Applied Physics Express,5(11):111201 201211
Kengo Takamiya, Toshiyuki Fukushima, Shuhei Yagi, Yasuto Hijikata, Toshimitsu Mochizuki, Masahiro Yoshita, Hidefumi Akiyama, Shigeyuki Kuboya, Kentaro Onabe, Ryuji Katayama, and Hiroyuki Yaguchi

Micro-Photoluminescence Study on the Influence of Oxidation on Stacking Faults in 4H-SiC Epilayers
,Applied Physics Express,5(5):051302 201205
Hikaru Yamagata, Shuhei Yagi, Yasuto Hijikata, and Hiroyuki Yaguchi

RF-MBE growth of semipolar InN(10-13) and InGaN(10-13) on GaAs(110)
,Physica Status Solidi C,Vol. 9(No. 3-4):658-661 201203
M. Orihara, S. Yagi, Y. Hijikata, and H. Yaguchi

Single Photon Generation from Nitrogen Atomic-Layer Doped Gallium Arsenide
,Materials Science Forum,706-709:2916-2921 2012
K. Takamiya, Y. Endo, T. Fukushima, S. Yagi, Y. Hijikata, T. Mochizuki, M. Yoshita, H. Akiyama, S. Kuboya, K. Onabe, R. Katayama and H. Yaguchi

Oxygen partial pressure dependence of the SiC oxidation process studied by in-situ spectroscopic ellipsometry
,Journal of Applied Physics,112(2):024502 2012
K. Kouda, Y. Hijikata, S. Yagi, H. Yaguchi, and S. Yoshida

TEM Analysis of Structural Phase Transition in MBE Grown Cubic InN on MgO (001) by MBE: Effect of Hexagonal Phase Inclusion in an C-GaN Nucleation Layer
,Applied Mechanics and Materials,229-231:219-222 2012
J. Parinyataramas, S. Sanorpim, C. Thanachayanont, H. Yaguchi, M. Orihara

Influence of off-cut angle of (0001) 4H-SiC on the crystal quality of InN grown by RF-MBE
,Procedia Engineering,32:882-887 2012
P. Jantawongrit, S. Sanorpim, H. Yaguchi, M. Orihara, P. Limsuwan

Single photon emission from nitrogen delta-doped semiconductors
SPIE,Proc. of SPIE,7945:79452F 2011
ISBN:doi: 10.1117/12.865770
H. Yaguchi
Isolated isolectronic traps in semiconductors are promising candidates for single-photon emitters because sharp emission lines with well-defined wavelengths are readily obtained. In this work, we study the emission from individual isoelectronic traps formed by nitrogen-nitrogen pairs in nitrogen delta-doped GaAs grown on (001) and (111)A substrates. We have found there is a remarkable difference in the polarization properties of luminescence for between (001) and (111) substrates, and successfully obtained unpolarized single photons by utilizing (111) substrate, which are desirable for the application to quantum cryptography. Unpolarized photons could also be obtained from nitrogen delta-doped GaAs/AlGaAs heterostructures grown on (001) substrates.

Theoretical studies for Si and C emission into SiC layer during oxidation
,Materials Science Forum,679-680:429-432 2011
Y. Hijikata, H. Yaguchi, and S. Yoshida
To understand the structure of SiC-oxide interface more in detail, we propose a profiling theory of Si and C emission into SiC layer during oxidation. Simulations of the depth profiles of Si and C interstitials results in the structures analogous with those observed from a spectroscopic ellipsometry. To determine the diffusivities of Si and C interstitials, we performed capacitance-voltage measurements for examining the re-distribution profiles of nitrogen after oxidation and compared between observed and calculated profile. The calculated nitrogen profiles showed good fits to the observed ones in the case of self-diffusivity of C interstitials magnified by several 10 times for literature value. Finally, we discuss the validity of the proposed theory.

Growth rate enhancement of silicon-carbide oxidation in thin oxide regime
,Properties and Applications of Silicon Carbide, Chapter 4, Edited by Rosario Gerhardt, InTech:77-87 2011
Y. Hijikata, H. Yaguchi and S. Yoshida

High Cubic-Phase Purity InN on MgO (001) Using Cubic-Phase GaN as a Buffer Layer
,AIP Conference Proceedings,1399:131-132 2011
S. Sanorpim, S. Kuntharin, J. Parinyataramas, H. Yaguchi, Y. Iwahashi, M. Orihara, Y. Hijikata, and S. Yoshida

In-situ Spectroscopic Ellipsometry Study of SiC Oxidation at Low Oxygen-Partial-Pressures
,Materials Science Forum,645-648:813-816 2010
K. Kouda, Y. Hijikata, H. Yaguchi, and S. Yoshida
We have investigated the oxidation process of SiC (000-1) C-face at low oxygen partial pressures using an in-situ spectroscopic ellipsometry. The oxide growth rate decreased steeply at the early stage of oxidation and then slowly decreased with increasing oxide thickness. The initial oxide growth rate was almost proportional to the oxygen partial pressure for both the polar directions. This result suggests that the initial interfacial reaction rate is constant regardless of the concentration of oxidants reaching the interface.
4H-SiC, in-situ, Si-C Emission Model, oxidation process, spectroscopic ellipsometry

Model calculations of SiC oxide growth rate at various oxidation temperatures based on the silicon and carbon emission model
,Materials Science Forum,645-648:809-812 2010
Y. Hijikata, H. Yaguchi, and S. Yoshida
We have tried to apply the oxidation model of SiC proposed previously, termed ‘Si-C emission model’, to the oxide growth rate at various oxidation temperatures. We have found that the model well reproduces the oxide thickness dependences of oxide growth rates for all of the temperatures measured for both of the SiC Si- and C-faces. We have estimated the temperature dependence of oxide depth profiles of Si and C interstitials by using the Si-C emission model, and discussed the structure at/near the SiC–oxide interface.
model calculation, oxidation, Deal-Grove model, silicon and carbon emission model

Photoluminescence from single isoelectronic traps in nitrogen delta-doped GaAs grown on GaAs(111)A
,Physica E,42(10):2529-2531 2010
T. Fukushima, Y. Hijikata, H. Yaguchi, S. Yoshida, M. Okano, M. Yoshita, H. Akiyama, S. Kuboya, R. Katayama, K. Onabe
We have studied photoluminescence (PL) observed from single isoelectronic traps formed by nitrogen pairs in nitrogen delta-doped GaAs layers grown on GaAs(111)A substrates. The PL was composed of a single peak with a narrow linewidth of ~80 micro eV. Polarized PL measurements confirmed that the emission from single isoelectronic traps in nitrogen delta-doped GaAs(111) is unpolarized irrespective of nitrogen pair arrangements. These results can be explained by in-plane isotropy of the samples, which is consistent with the symmetrical property of GaAs(111), and demonstrate that utilizing (111) substrate is an effective means for obtaining unpolarized single photons, which are desirable for the application to quantum cryptography.
Isoelectronic trap, Single photon, delta-doping

RF-MBE growth of InN on 4H-SiC (0001) with off-angles
,Physica Status Solidi C,7(7-8):2016-2018 2010
M. Orihara, S. Takizawa, T. Sato,Y. Ishida, S. Yoshida, Y. Hijikata, and H. Yaguchi
We have grown InN on 4H-SiC (0001) substrates with various off-angles by RF-N2 plasma molecular beam epitaxy (RF-MBE). Scanning electron microscope observation revealed that InN films grown on 4H-SiC (0001) substrates with off-angles of 4°and 8° are very smooth and that there are no voids which have often observed for InN epitaxial layers. X-ray diffraction reciprocal space maps for InN grown on 4H-SiC (0001) showed that the c-axes of InN grown on 4H-SiC 4° and 8° off substrates are inclined by 0.35° and 0.8°, respectively, toward the misorientation of the substrate while the c-axis of InN is parallel to that of 4H-SiC for the on-axis substrate. Strong PL peak was observed from InN grown on 4° off substrate at 0.68 eV at 15 K. The PL peak was clearly observed even at room temperature and simply shifted to lower energies with increasing temperature. The difference in the PL peak energy between at 15 K and 300 K was 20 meV, which is reasonable taking into account the difference in the thermal coefficients of InN and SiC.
InN, MBE, growth, structure, photoluminescence

A Kinetic Model of Silicon Carbide Oxidation Based on the Interfacial Silicon and Carbon Emission Phenomenon
,Applied Physics Express,2(2):021203 2009
Y. Hijikata, H. Yaguchi, and S. Yoshida
We proposed a kinetic model for thermal oxidation of silicon carbide, termed "silicon and carbon emission model", taking into account the Si and C emissions from the oxidation interface, which lead to a reduction of interfacial reaction rate. We used this model to calculate oxide growth rates and found that the derived growth rates showed a good fit with the measured rates over the entire oxide thickness for both the C and Si faces. We discussed the difference in oxidation mechanism between these polar faces in terms of the difference in parameter values deduced from the curve fits.

Characterization of 4H-SiC-SiO2 Interfaces by a Deep Ultraviolet Spectroscopic Ellipsometer
,Materials Science Forum,615-617:505-508 2009
H. Seki, T. Wakabayashi, Y. Hijikata, H. Yaguchi, and S. Yoshida
We have characterized 4H-SiC-oxide interfaces fabricated by thermal oxidation of SiC using spectroscopic ellipsometry in the wide spectral range from visible to deep UV region. It was found that there exists an interface layer, around 1 nm in thickness, regardless of the oxide thickness from 15 nm to 40 nm. The optical constants of the interface layer have similar spectral dependence to those of SiC, though the absolute value of the refractive indices is 0.5-1 larger than that of SiC. We have discussed the structure of the interface layer based on the oxidation mechanism of SiC, like the Si-emission model.
4H-SiC, Refractive Index, Si Emission Model, SiC-SiO2 Interface, Spectroscopic Ellipsometry (SE)

Model Calculation of SiC Oxidation Rates in the Thin Oxide Regime
,Materials Science Forum,600-603:663-666 2009
Y. Hijikata, T. Yamamoto, H. Yaguchi and S. Yoshida
To explain the growth rate enhancement of SiC oxidation in the thin oxide regime, which was recently found from the real time monitoring experiments of the initial oxidation stage of SiC (000–1) C-face using an in-situ spectroscopic ellipsometer, we tried to apply the interfacial Si emission model, which has been originally proposed for Si oxidation, and found that the Si emission model successfully reproduced the SiC oxidation rates at the whole range of oxide thickness and at oxidation temperatures measured. By comparing with the simulations for Si oxidation, we have discussed the oxidation mechanism of SiC.
Deal-Grove Model, Growth Enhancement, Model Calculation, Oxidation, Si Emission Model

Model Calculation of SiC Oxide Growth Rate Based on the Silicon and Carbon Emission Model
Trans Tech Publications,Materials Science Forum,615-617:489-492 2009
Y.Hijikata, H.Yaguchi, and S.Yoshida
We proposed a kinetic model for SiC oxidation, named 'silicon and carbon (Si-C) emission model', taking into account the emission of Si and C atoms from the SiC-oxide interface, which suppresses the oxidation rate at the interface. Based on the model, we calculated oxide growth rates for SiC (0001) Si- and (000-1) C-face and found that the calculated values exhibit good fits to the measured ones in the entire oxide thickness range for both faces. We also calculated depth profiles of Si and C interstitials and oxidants, and discussed the oxidation mechanism of SiC as well as the difference in the oxidation process of Si-face and C-face.
Deal-Grove Model, Growth Rate Enhancement, Model Calculation, Oxidation, Si Emission Model

Observation of SiC Oxidation in Ultra-thin Oxide Regime by In-situ Spectroscopic Ellipsometry
Trans Tech Publications,Materials Science Forum,615-617:509-512 2009
T.Takaku, Y.Hijikata, H.Yaguchi and S.Yoshida
Thermal oxidation process of silicon carbide in ultra-thin oxide regime has been studied by performing in-situ and real time spectroscopic ellipsometry. We found the thermal oxidation at 700C forms no or extremely thin interface layers between SiC and oxide layers. In contrast, the oxidation at 850C forms an interface layer of around 1 nm in thickness, having similar thickness and optical constants of the interface layers formed by the oxidation at higher temperature than 1000C. To make clear the conditions no interface layer is formed, i.e., whether low temperature growth or thin oxide thickness is crucial, we have performed the oxidation at 850C in the reduced oxygen pressure. Based on the results of these experiments, we discussed the origin of the formation of interface layers as well as the oxidation mechanism of SiC.
(0001), 4H-SiC, In Situ Spectroscopic Ellipsometry, Interface Layer, Optical Constant, Oxidation, Si Emission Model

Optical and electrical characterizations of 4H-SiC oxide interfaces by spectroscopic ellipsometry and capacitance voltage measurements
Elsevier,Applied Surface Science,255(20):8648-8653 2009
H.Hashimoto, Y.Hijikata, H.Yaguchi and S.Yoshida
4H-SiC–oxide interfaces formed by various oxidation methods on SiC (0001) Si- and (000-1) C-face substrates have been characterized by performing spectroscopic ellipsometry in wide spectral region including deep UV spectral range and capacitance–voltage measurements. The results exhibit that the refractive indices of the interface layers well correlate with interface state density in all the cases of oxidation processes. To investigate the difference in interface characteristics between wet and dry oxidation, we compared to the sample fabricated by wet oxidation followed by heating in Ar or O2 atmosphere, aiming to remove hydrogen related species at the interface. We also tried to make clear the difference in the interface characteristics between Si- and C-faces by lowering the oxidation rate of C-face down to those for Si-face. Putting together with all of the results obtained, we discuss the origins that determine the interface characteristics in terms of both the optical and electrical characterizations.
4H-SiC; Spectroscopic ellipsometry; C–V measurements; Dry and wet oxidation; 4H-SiC–oxide interface; Interface state density

Oxygen-Partial-Pressure Dependence of SiC Oxidation Rate Studied by In-situ Spectroscopic Ellipsometry
,Materials Science Forum,600-603:667-670 2009
T. Yamamoto, Y. Hijikata, H. Yaguchi and S. Yoshida
Real time observations of SiC (000–1) C-face and (0001) Si-face oxidation were performed using an in-situ ellipsometer over the oxygen-partial-pressure range from 0.1 to 1.0 atm. We analyzed the relations between oxide growth rate and oxide thickness by applying an empirical relation proposed by Massoud et al. We found the occurrence of oxidation enhancement in the thin oxide regime also for Si-face as well as for C-face. We have discussed the oxygen-partial-pressure dependence of the oxidation rate constants between SiC C- and Si face, comparing with that of Si.
(0001), (000-1), In-Situ Spectroscopic Ellipsometry, Deal-Grove Model, Massoud Empirical Relation, Oxidation, Silicon Carbide (SiC)

High Resolution X-ray Diffraction and Raman Scattering Studies of Cubic-phase InN Films Grown by MBE
,Advanced Materials Research,55-57:773-776 2008
S. Kuntharin, S. Sanorpim, H. Yaguchi, Y. Iwahashi, M. Orihara, Y. Hijakata and S. Yoshida
We demonstrate the use of high resolution X-ray diffraction and Raman scattering to assess the generation of hexagonal-phase in the cubic-phase InN (c-InN) films on MgO substrates grown by molecular beam epitaxy with a cubic-phase GaN buffer layer. The X-ray reciprocal-lattice space mapping was used to examine the hexagonal-phase generated on the cubic (111) planes in the c-InN films. Ratio of hexagonal to cubic components in the c-InN grown layers was estimated from the ratio of the integrated X-ray diffraction intensities of cubic (002) and hexagonal (10-11) reflections measured by ω-scans. Amount of hexagonal-phase presented in the c-InN films was determined in the range of 6 to 24%. It was found that the Raman characteristics are also sensitive to hexagonal-phase presented in the c-InN films. For the lowest amount of hexagonal-phase (6%), only Raman scattering characteristics of c-InN was observed, indicating formation of a small amount of stacking faults, which not affected on the vibrational property. Based on our results, relatively easy access to the generation of hexagonal-phase suggests that it may be very useful for HRXRD and Raman scattering measurements of c-InN.

Improvement of the surface morphology of a-plane InN using low-temperature InN buffer layers
,Physica Status Solidi (c),5(6):1808-1810 2008
G. Shikata, S. Hirano, T. Inoue, M. Orihara, Y. Hijikata, H. Yaguchi and S. Yoshida
We report on the improvement of the surface morphology of a-plane InN films grown by RF molecular beam epitaxy. By using low-temperature (LT) InN buffer layers, we could successfully obtain InN films with a smooth surface. The full width at half maximum values of the x-ray diffraction (11-20) rocking curve along the [0001] InN direction were 2870 arcsec and 3410 arcsec for a-plane InN samples grown at 500°C with and without LT-InN buffer layers, respectively. Thus, we could improve also the crystalline quality of a-plane InN films by using LT-InN buffer layers. We observed strong polarization anisotropy in the photoluminescence spectra of a-plane InN, which is typical of nonpolar wurtzite III-nitride films.

Oxide Growth Rate Enhancement of Silicon Carbide (0001) Si-Faces in Thin Oxide Regime
,Japanese Journal of Applied Physics,47(10):7803-7806 2008
T. Yamamoto, Y. Hijikata, H. Yaguchi and S. Yoshida
Thermal oxidation process of silicon carbide (SiC) has been studied by performing in-situ spectroscopic ellipsometry. In our previous work, we, for the first time, found that the growth rates of SiC(000-1) C-face at oxidation thicknesses less than around 20 nm are much higher than those given by the Deal-Grove (D-G) model. In this report, we show that such a growth rate enhancement occurs also in the oxidation of SiC(0001) Si-face. By applying the empirical equation proposed by Massoud et al. [J. Electrochem. Soc. 132 (1985) 2685] to the oxidation of SiC Si-face and comparing the temperature and oxygen partial pressure dependences of oxidation rate parameters obtained with those for C-face, we discuss the difference in oxidation mechanism between SiC Si- and C-faces.
silicon carbide (SiC), (0001) Si-face, oxidation, in-situ spectroscopic ellipsometry, Deal–Grove model, Massoud empirical equation

Photoluminescence of cubic InN films on MgO (001) substrates
,Physica Status Solidi (c),5(6):1579-1581 2008
T. Inoue, Y. Iwahashi, S. Oishi, M. Orihara, Y. Hijikata, H. Yaguchi and S. Yoshida
We have studied photoluminescence from cubic InN films grown on MgO substrates with a cubic GaN underlayer by RF N2 plasma molecular beam epitaxy. A single PL peak was observed at 0.47 eV. By analyzing the reflectance spectra of cubic InN films, we could derive the refractive index and extinction coefficient, and found the band gap energy of cubic InN is 0.48 eV, indicating that the PL peak observed at 0.47 eV is due to the interband transition of cubic InN. The difference in the PL peak energy between hexagonal and cubic InN is in good agreement with that predicted by ab-initio calculations.

Photoluminescence study of hexagonal InN/InGaN quantum well structures grown on 3C-SiC (001) substrates by molecular beam epitaxy
,Physica Status Solidi (c),5(6):1730-1732 2008
S. Hirano, T. Inoue, G. Shikata, M. Orihara, Y. Hijikata, H. Yaguchi, S. Yoshida and Y. Hirabayashi
We have studied photoluminescence from hexagonal InN/InGaN multiple quantum well structures grown on 3C-SiC (001) substrates with an InGaN underlayer by plasma assisted molecular beam epitaxy. We have observed photoluminescence spectra of InN/InGaN MQWs with various well widths. The photoluminescence peak related to quantum wells was clearly observed even at room temperature and found to shift to higher energies with decreasing well width due to the quantum confinement effect. We also discuss the effect of the built-in electric fields on the PL peak energy.

Twin photoluminescence peaks from single isoelectronic traps in nitrogen delta-doped GaAs
,Physica E-Low-Dimensional Systems & Nanostructures,40(6):2110-2112 2008
Y. Endo, Y. Hijikata, H. Yaguchi, S. Yoshida, M. Yoshita, H. Akiyama, F. Nakajima, R. Katayama and K. Onabe
We report on twin emission peaks observed from single isoelectronic traps formed by nitrogen pairs in nitrogen delta-doped GaAs by high-energy resolution micro-photoluminescence (PL) spectroscopy. The twin PL peaks show almost the same intensity with narrow linewidths of 20-50 mu eV, which are considerably smaller than that ever reported for isoelectronic traps in GaAs:N. The higher and lower energy luminescence transitions were linearly polarized in the [1 (1) over bar 0] and [1 1 0] directions, respectively, indicating that the two exciton states have completely orthogonal relations with each other. The fact that any pair of the twin PL peaks has the same polarization properties suggests that the splitting is due to the anisotropy between [1 (1) over bar 0] and [1 1 0] directions in the host crystal and is possibly explained by the strain anisotropy in the sample.

Simultaneous Determination of the Carrier Concentration, Mobility and Thickness of SiC Homo-Epilayers Using Terahertz Reflectance Spectroscopy
,Materials Science Forum,556-557:423-426 2007
S. Oishi, Y. Hijikata, H. Yaguchi and S. Yoshida
We have simultaneously determined the carrier concentration, mobility, and thickness of 4H-SiC homo-epilayers with carrier concentration of 1016–1018 cm-3 from reflectance spectroscopy in the wavenumber range of 20–2000 cm-1. The spectra at 20–100 cm-1 and at 80–2000 cm-1 were measured by using the terahertz time domain spectrometer (THz-TDS) and the Fourier-transform infrared (FTIR) spectrometer, respectively. A modified classical dielectric function (MDF) model was employed for the curve fitting. We have compared the values of free carrier concentrations estimated from the reflectance spectroscopy with the net doping concentrations obtained from C–V measurements, and have discussed the validity of the electrical properties estimated from the reflectance spectroscopy.
Capacitance to Voltage Measurement, Carrier Concentration, Hall-Effect Measurement, Homo-Epilayer, Infrared Reflectance Spectroscopy, Mobility, Terahertz Infrared Spectroscopy

Structural and optical characterization of high In content cubic InGaN on GaAs(001) substrates by RF-MBE
,Physica Status Solidi (c),4(7):2437-2440 2007
T. Nakamura, Y. Endo, R, Katayama, H. Yaguchi and K. Onabe
High In content cubic InGaN films have been successfully grown on GaAs(001) substrates by rf-plasma assisted molecular beam epitaxy (RF-MBE). The X-ray diffraction analysis has confirmed the Ga content of the cubic InGaN films increases with increasing the group-III flux ratio (Ga/(Ga+In)). The maximum Ga content of the c-InGaN film is about 29% based on an analysis of the X-ray diffraction 2theta/omega scan. By 2theta/omega and omega X-ray reciprocal space mapping measurements, hexagonal-phase ande twin-phase InGaN are found to be generated from c-InGaN{111} factes. By low temperature PL measurement, the c-In1-xGaxN peak shifts from 0.41 eV (x=0) to 0.72 eV (x=0.09) with increasing Ga content, showing that the band-gap of c-InGaN is ~300 meV smaller that that of h-InGaN with the same alloy composition.

閃亜鉛鉱構造窒化物半導体のエピタキシャル成長
,日本結晶成長学会誌,34(4):201-206 2007
矢口裕之
We have studied photoluminescence from cubic InN films grown on MgO substrates with a cubic GaN underlayer by RF N2 plasma molecular beam epitaxy. A single PL peak was observed at 0.47 eV. By analyzing the reflectance spectra of cubic InN films, we could derive the refractive index and extinction coefficient, and found the band gap energy of cubic InN is 0.48 eV, indicating that the PL peak observed at 0.47 eV is due to the interband transition of cubic InN. The difference in the PL peak energy between hexagonal and cubic InN is in good agreement with that predicted by ab-initio calculations.

Growth Rate Enhancement of (000-1)-Face Silicon-Carbide Oxidation in Thin Oxide Regime
,Japanese Journal of Applied Physics,46(32):L770-L772 2007
T. Yamamoto, Y. Hijikata, H. Yaguchi and S. Yoshida
The thermal oxidation of silicon carbide (SiC) has been studied by performing in-situ ellipsometry. We have found that the oxidation rates at the oxidation thickness of approximately less than around 20 nm are much larger than those given using the Deal-Grove (D-G) model, suggesting that the oxidation time dependence of the oxide thickness cannot be explained using the D-G model, i.e., a simple linear-parabolic model, in the initial oxidation stage. By using the empirical relation, which has been proposed for Si oxidation, i.e., adding an exponential term to the D-G equation, the origin of the growth rate enhancement in SiC oxidation has been discussed.
silicon carbide (SiC), (0001) C-face, oxidation, in-situ ellipsometry, Deal–Grove model, Massoud empirical equation

Micro-photoluminescence study of nitrogen delta-doped GaAs grown by metalorganic vapor phase epitaxy
Elsevier,Journal of Crystal Growth,298:73-75 2007
Y. Endo, K. Tanioka, Y. Hijikata, H. Yaguchi, S. Yoshida, M. Yoshita, H. Akiyama, W. Ono, F. Nakajima, R. Katayama and K. Onabe
We have measured micro-photoluminescence (PL) spectra of nitrogen delta-doped GaAs with various concentrations. In nitrogen delta-doped GaAs with low concentrations, the micro-PL spectra measured at different positions were individually different. In contrast, almost the same spectra were obtained for nitrogen d-doped GaAs with higher concentrations and uniformly nitrogen-doped GaAs. The micro-PL study shows that there are no more than a few isoelectronic traps within a diameter of ~1 mm. This indicates a good prospect for applications of isoelectronic traps to single photon emitting devices.
Doping optical microscopy,. Metalorganic vapor phase epitaxy, Semiconducting III–V materials

Micro-Raman study on the improvement of luminescence efficiency of GaAsN alloys
Elsevier,Journal of Crystal Growth,298:131-134 2007
K. Tanioka, Y. Endo, Y. Hijikata, H. Yaguchi, S. Yoshida, N. Yoshita, H. Akiyama and K. Onabe
We have used in situ micro-Raman spectroscopy to clarify the mechanism of the luminescence efficiency improvement of GaAsN alloys by laser irradiation. Raman peak intensity of GaAs-like longitudinal optical (LO) mode phonon was observed to increase with the laser irradiation time. With increasing laser power density, the Raman intensity of GaAs-like LO mode phonon was found to increase more rapidly and to be saturated in a shorter time. Changes in the Raman intensity can be expressed by the same equation used for the luminescence efficiency improvement. Time constants of changes in the Raman intensity were almost in agreement with those of the luminescence efficiency improvement. This indicates that the increase in Raman intensity of GaAs-like LO phonon is closely related to the luminescence efficiency improvement.
Defects, Optical microscopy, Metalorganic vapor phase epitaxy, Alloys, Semiconducting III–V materials

Modulation spectroscopic investigation on lattice polarity of gallium nitride
American Institute of Physics,Applied Physics Letters,91(6):061917 2007
R. Katayama, K. Onabe, H. Yaguchi, T. Matsushita and T. Kondo
A lattice polarity determination method for GaN is demonstrated, which is based on a capability of modulation spectroscopy for the assignment of electric-field directions performed nondestructively using simple optical setups. A strong spontaneous polarization induces an upward band bending toward +c surfaces and a downward but weaker bending toward -c surfaces for typical films with small residual strains and electron densities. This difference is distinguishable in terms of the spectral-phase flip, utilizing photoreflectance, and electroreflectance. Quantitative analysis revealed the exciton dissociation at a high-field region of +c surfaces consistent with the band profile derived as a solution of Poisson equation.

Photoluminescence study of isoelectronic traps in dilute GaAsN alloys
Wiley,Physica Status Solidi (c),4(7):2760-2763 2007
H. Yaguchi, T. Aoki, T. Morioke, Y. Hijikata, S. Yoshida, M. Yoshita, H. Akiyama, D. Aoki and K. Onabe
We have studied photoluminescence spectra in detail to clarify the character of the isoelectronic traps in dilute GaAsN alloys. Several sharp lines have been observed at the lower energy side of the GaAs bandgap and are in good agreement with the nitrogen pair-related emission lines previously reported. In addition to the nitrogen pair-related lines, some other emission lines have been also observed. Compared with the energies of these emission lines and the nitrogen pair-related emission lines, it was found that the energy differences agree with the longitudinal optical phonon energy at the Γ point of GaAs, showing that the character of isoelectronic traps due to nitrogen pairs in dilute GaAsN alloys is significantly contributed from the conduction band state at the Γ point. The temperature dependence of the peak energy of luminescence due to nitrogen pairs also indicates that the character of isoelectronic traps in dilute GaAsN alloys is due to the conduction band edge state at the Γ point of GaAs. For a dilute GaAsN alloy with lower nitrogen concentration, we have observed that the intensity of an emission line increased superlinearly with excitation power.

RF-MBE growth of a-plane InN on r-plane sapphire with a GaN underlayer
Elsevier,Journal of Crystal Growth,301/302:517-520 2007
G. Shikata, S. Hirano, T. Inoue, M. Orihara, Y. Hijikata, H. Yaguchi and S. Yoshida
a-plane InN films were grown on r-plane sapphire substrates with GaN underlayers by RF-N2 plasma molecular beam epitaxy (MBE). X-ray diffraction (XRD) measurements and reflection high-energy electron diffraction (RHEED) observation revealed that the InN films were grown with InN (1 1 -2 0) || GaN (1 1 -2 0) || sapphire (2 -2 0 4). We have carried out micro-Raman scattering measurements for a-plane InN film. Raman peaks were observed at 448, 490 and 598 cm-1, which can be identified as the A1 transversal optical (TO), E2 (high) and E1 longitudinal optical (LO) mode phonon, respectively. We also carried out photoluminescence (PL) measurements for a-plane InN film. Strong PL was observed between 0.62 and 0.65 eV, which is the lowest ever reported for InN. It is suggested from the excitation intensity and temperature dependence of the PL spectra that the red shift of the PL peak is due to the Franz-Keldysh effect.

RF-MBE growth of InN/InGaN quantum well structures on 3C-SiC substrates
Elsevier,Journal of Crystal Growth,301/302:513-516 2007
S. Hirano, T. Inoue, G. Shikata, M. Orihara, Y. Hijikata, H. Yaguchi and S. Yoshida
InN/In0.83Ga0.17N multiple quantum well (MQW) structures have been fabricated on 3C-SiC (0 0 1) substrates by radio-frequency plasma-assisted molecular beam epitaxy (RF-MBE). The surface morphology, structural properties, and optical properties of the samples were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL), respectively. XRD satellite peaks due to the periodic structure were clearly observed in the MQW structures grown at temperatures lower than 530 C. PL emissions from the MQW were observed around 0.85 eV.
X-ray diffraction, Molecular beam epitaxy, Quantum wells, Nitrides, Semiconducting III–V materials

Characterization of Oxide Films on 4H-SiC Epitaxial (000-1) Faces by High-Energy-Resolution Photoemission Spectroscopy: Comparison between Wet and Dry Oxidation
,Journal of Applied Physics,100:053710 2006
Y. Hijikata, H. Yaguchi, S. Yoshida, Y. Takata, K. Kobayashi, H. Nohira and T. Hattori
Wet and dry oxide films-4H-SiC epitaxial (000-1) C-face interfaces have been characterized by capacitance-voltage (C-V) measurements and soft x-ray excited photoemission spectroscopy (SX-PES) and hard x-ray excited photoemission spectroscopy (HX-PES) using synchrotron radiation. The interface state density for wet oxidation is much smaller than that for dry oxidation at any energy level. In the PES measurements, intermediate oxidation states such as Si1+ and Si3+ were observed. In addition, the areal densities of these states were found to be in a good correspondence with those of the interface states. The reasons for the good electrical characteristics of metal-oxide-semiconductor devices fabricated by wet oxidation are discussed in terms of the depth profiles of oxide films derived from the SX-PES and HX-PES results.

Off-Angle Dependence of Characteristics of 4H-SiC-Oxide Interfaces
,Materials Science Forum,527-529:1003-1006 2006
Y. Hijikata, H. Yaguchi, S. Yoshida, Y. Takata, K. Kobayahi, H. Nohira, and T. Hattori
SiC-Oxide interfaces on 4H-SiC epitaxial substrates of various off-angles have been characterized by C-V measurements, synchrotron radiation excited photoemission spectroscopy and atomic force microscopy. We found that the interface state density (Nit ) and the amount of sub-oxides (Si) for small off-angle substrates were smaller than those for large off-angle ones. It was also found that there is a good correlation between the amount of the interface states and that of sub-oxides. Step-terrace structures were clearly observed in the surface morphology after the removal of oxide layers for small off-angle substrates, which shows that the interfaces were atomically smooth. These results suggest that the small Nit and Si values for small off-angle substrates relate to the smoothness of the interface and that high performance SiC MOS devices are expected by using small off-angle substrates.
(000-1) C-Face, Capacitance-Voltage, Dry Oxidation, Interface States (or Traps), Off-Angle, Oxide-SiC Interface, Photomission spectroscopy, Suboxide, Wet Oxidation

Photo-induced improvement of radiative efficiency and structural changes in GaAsN alloys
,Physica Status Solidi (c),3(6):1907-1910 2006
H. Yaguchi, T. Morioke, T. Aoki, H. Shimizu, Y. Hijikata, S. Yoshida, M. Yoshita, H. Akiyama, N. Usami, D. Aoki and K. Onabe
We have investigated the excitation power density and nitrogen concentration dependence of the changes in the radiative efficiency of GaAsN alloys to examine the mechanism of the photo-induced improvement of radiative efficiency. With increasing excitation power density, the radiative efficiency increased more rapidly. The measure of the improvement Iafter/Ibefore superlinearly increased with increasing nitrogen concentration x up to ~1%. This suggests that the nonradiative recombination centers eliminated by photoexcitation are not defects formed by a single nitrogen atom but complexes formed by gathering of several nitrogen atoms. Micro Raman study revealed that the GaAs-like LO mode phonon peak intensity increased with photoexcitation time in a similar way to the increase in the radiative efficiency. Considering that this phenomenon is in a time scale of several seconds, the photo-induced structural changes correspond not to long range inter-diffusion but to local changes in atomic configuration which lead to the decrease in the density of nonradiative recombination centers.

Real Time Observation of SiC Oxidation using In-Situ Ellipsometer
,Materials Science Forum,527-529:1031-1034 2006
K. Kakubari, R. Kuboki, Y. Hijikata, H. Yaguchi and S. Yoshida
Real time observation of SiC oxidation was performed using an in-situ ellipsometer over the temperature range from 900°C to 1150°C. The relations between oxide thickness and oxidation time were obtained precisely by virtue of the real time measurements. We analyzed the relations between oxide thickness and oxidation time by applying the Deal and Grove model to obtain the linear and parabolic rate constants. Taking advantage of in-situ measurements, we successfully obtained the oxidation rate constants with high accuracy.
4H-SiC, Activation Energy, In Situ Ellipsometer, Linear Oxidation Rate Constant, Oxidation, Oxide-SiC Interface, Parabolic Oxidation Rate Constant

RF-MBE growth of cubic InN films on MgO (001) substrates
,Physica Status Solidi (c),3(6):1515-1518 2006
Y. Iwahashi, H. Yaguchi, A. Nishimoto, M. Orihara, Y. Hijikata, S. Yoshida
Cubic InN films have been grown on MgO substrates with cubic GaN underlayers by RF-N2 plasma MBE. By changing the growth conditions, we clarified the growth temperature and In flux dependence of the quality of cubic InN films. It was found the surface of cubic InN films grown at relatively higher tem- peratures was smooth and that the hexagonal phase content in the InN films decreased with increasing In flux. Based on the findings, we have successfully obtained a c-InN film with high phase-purity and a smooth surface. We have carried out micro Raman scattering measurements for the high-quality cubic InN film. Raman peaks were clearly observed at 596 cm-1 and 467 cm-1 , which are attributed to longitudinal optical and transverse optical phonon modes of cubic InN, respectively.

Simultaneous Determination of Carrier Concentrations, Mobilities and Thickness of SiC Homo-Epilayers Using Infrared Reflectance Spectroscopy
,Japanese Journal of Applied Physics,45:L1226-L1229 2006
S. Oishi, Y. Hijikata, H. Yaguchi and S. Yoshida
We have simultaneously determined the carrier concentration, mobility, and thickness of 4H-SiC homoepilayers with carrier concentrations of 1017 - 1018 cm-3 from infrared reflectance measurements with the wave number range of 80 - 2000 cm-1. A modified classical dielectric function model was employed for the fitting analyses. We have prepared n-type epilayers on p-type and n-type substrates for comparison with the values of the carrier concentration and mobility estimated from infrared reflectance measurements with those obtained from Hall-effect measurements and C-V measurements. Through these comparisons, we have confirmed the validity of the values estimated from infrared reflectance measurements.
SiC, homoepilayer, infrared reflectance, nondestructive and contactless measurement, carrier concentration, mobility, Hall-effect measurement, capacitance–voltage measurement

Characterization of Oxide Films on SiC Epitaxial (000-1) Faces by Angle-Resolved Photoemission Spectroscopy Measurements using Synchrotron Radiation
,Materials Science Forum,483-485:585-588 2005
Y. Hijikata, H. Yaguchi, S. Yoshida, Y. Takata, K. Kobayashi, S. Shin, H. Nohira and T. Hattori
Thermal oxide films on SiC epitaxial (000-1) C-faces have been characterized by angle-resolved photoemission spectroscopy (AR-PES). The structure of wet oxide/SiC C-face interface was compared with that of dry oxide/SiC C-face, as well as that of dry oxide/SiC Si-face, in order to clarify why a MOS device of SiC C-face achieved good electrical properties. The improvement in electrical properties was confirmed by AR-PES measurements, evidencing differences in binding energy between SiC and the Si4+ components in Si2p and valence band region, and in binding energy between SiC and the CHx components in C1s. The reason for the improvement in electrical property of MOS devices by use of SiC C-face are discussed in terms of depth profiles of oxide films calculated from the AR-PES results.
(000-1) Face, Bonding, Dry Oxidation, Oxide/SiC Interface, Photoelectron Spectroscopy, Wet Oxidation

Effect of Ar Post-Oxidation Annealing on Oxide-4H-SiC Interfaces Studied by Capacitance to Voltage Measurements and Photoemission Spectroscopy
,Journal of Vacuum Science and Technology A,23(2):298-303 2005
Y. Hijikata, H. Yaguchi, Y. Ishida, M. Yoshikawa and S. Yoshida
The effect of post-oxication annealing in Ar atmosphere (Ar POA) on 4H-SiC-oxide interfaces has been studied by capacitance to gate-bias voltage (C-V) measurements and photoemission spectroscopy (PES). It was found from the C-V measurements that the shift of the C-V curve disappears when the Ar POA tempeature is higher than 600 C. On the other hand, angle-resolved x-ray photoelectron spectroscopy measurements revealed that the thickness of the intermediate layers containing Si1+ oxidation states observed at the interfaces decreases abruptly when the Ar POA temperature exceeds 500 C. In ultraviolet photoelectron spectra, O2p peaks were changed by Ar POA at temperatures higher than 600 C, which is the temperature where the shift of the C-V curve disappears in C-V measurements. This shows that the change in O2p bonding by Ar POA is the origin of the shift observed in C-V characteristics. A model of structural changes in the interfaces by Ar POA has been proposed based on the results of PES measurements and those of C-V measurements.

Growth of high-quality hexagonal InN on 3C-SiC (001) by molecular beam epitaxy
,Physica Status Solidi (c),2(7):2267-2270 2005
H. Yaguchi, Y. Kitamura, K. Nishida, Y. Iwahashi, Y. Hijikata and S. Yoshida
We have grown hexagonal InN (h-InN) films on 3C-SiC (001) substrates by RF-N2 plasma molecular beam epitaxy taking account of small lattice mismatch between h-InN (10-10) and 3C-SiC (110). It was found from X-ray diffraction (XRD) measurements that h-InN grows with h-InN (0001) || 3C-SiC (001) and h-InN (1-100) || 3C-SiC (110). XRD measurements also revealed that the h-InN epitaxial layers grown on 3C-SiC (001) are composed of single domain. Strong and sharp photoluminescence from the h-InN was clearly observed at around 0.69 eV.

Characterization of carrier concentration and mobility in n-type SiC wafers using infrared reflectance spectroscopy
,Japanese Journal of Applied Physics,43(8A):5151-5156 2004
K. Narita, Y. Hijikata, H. Yaguchi, S. Yoshida and S. Nakashima
We have estimated the free-carrier concentration and drift mobility in n-type 6H-SiC wafers in the carrier concentration range of 1017 -1019 cm-3 from far- and mid-infrared (30-2000 cm-1) reflectance spectra obtained at room temperature. A modified classical dielectric function model was employed for the analysis. We found good agreement between the electrical propertiesderived from infrared reflectance spectroscopy and those derived from Hall effect measurements. We have demonstrated the spatial mapping of carrier concentration and mobility for commercially produced 2 inch SiC wafers.
SiC, infrared reflectance, Hall measurement, electrical properties, carrier concentration, drift mobility, Hall mobility

Characterization of electrical properties in high-dose implanted and post-implantation-annealed 4H-SiC wafers using infrared reflectance spectroscopy
,Materials Science Forum,457-460:905-908 2004
K. Narita, Y. Hijikata, H. Yaguchi, S. Yoshida, J. Senzaki, S. Nakashima
Infrared reflectance speoctroscopy has been used to characterize the electrical properties and crystalline damage of high-dose implanted and post-implantation-annealed 4H-SiC. The carrier concentration, mobility and crystalline damage were independently derived from the analysis of the infrared reflectance spectra using the effective medium approximation and the modified dielectric function taking into acocunt the TO and LO phonon damping factors independently. The carrier concentration and mobility in the recrystallized SiC derived from infrared reflectance spectra are in good agreement with those obtained from Hall effect measurements. The annealing temperature depencence of crystalline damage suggests that the impurities are almost activated by the annealing at a temperature as low as 1200 C for 30 min, though the crystallinity of the implanted layer is improved with increasing annealing temperature. In addition, it is revealed that the annealing at a temperature as high as 1700C recovers the crystallinity of the implanted layer within 1 min. These results demonstrate that the infrared reflectance spectroscopy is a useful technique to characterize both the electrical properties and crystallined damage of implanted and post-implantation-annealed layers in SiC wafers simultaneously.
4H-SiC, Activation Anneal, Carrier Concentration, Crystalline Damage, Hall Measurements, Infrared Reflectance Spectroscopy, Ion Implantation, Mobility

Epitaxial growth of hexagonal and cubic InN films
,Physica Status Solidi (b),241(12):2839-2842 2004
K. Nishida, Y. Kitamura, Y. Hijikata, H. Yaguchi and S. Yoshida
We have grown InN films on 3C-SiC (001) substrates with and without cubic GaN underlayers by RF-N2 plasma MBE. It was found that, in the case of direct growth on 3C-SiC (001), hexagonal InN grows with the crystal orientation as hexagonal InN(1100)//3C-SiC(110), while, in the case of the growth on cubic GaN underlayers, cubic InN grows with the crystal orientation as cubic InN (110)//cubic GaN (110). Photoluminescence emissions from the cubic and hexagonal InN films were clearly observed at around 0.7 eV.

Photoemission spectroscopic studies on oxide/SiC interfaces formed by dry and pyrogenic oxidation
,Materials Science Forum,457-460:1341-1344 2004
Y. Hijikata, H. Yaguchi, Y. Ishida, M. Yoshikawa, T. Kamiya and S. Yoshida
The difference in the structure of oxide/SiC interface between dry and pyrogenic oxidation and the effect of post-oxidation annealing in Ar atmosphere on the interfaces have been studied by X-ray and ultraviolet photoelectron spectroscopy to make clear tha interface structures which spoil the electrical properties. It is found that intermediate layers containing Si1+ oxidation states exist in both cases of oxidation method and the thickness of the layer changes by Ar annealing. It is also found that the oxide/SiC band offsets and the structures of O2p peak, observed in valence band spectra, change remarlably by Ar POA in both cases of oxidation method. The bond states at SiC/oxide interfaces have been discussed by considering these results together with the results from C-V measurements.
10.4028/www.scientific.net/MSF.457-460.905

Improvement in the luminescence efficiency of GaAsN alloys by photoexcitation
,Physica Status Solidi (b)(7):2782-2784 2003
H. Yaguchi , T. Morioke, T. Aoki, Y. Hijikata, S. Yoshida, H. Akiyama, N. Usami, D. Aoki, and K. Onabe
We found that photoexcitation with high excitation power density at low temperatures improves the luminescence efficiency of GaAsN alloys. From the temporal change of the PL intensity, the improvement occurs in a few minutes. Micro Raman study shows that structural changes occur in the laser-irradiated region. These indicate that the improvement of luminescence properties is due to photoexcitation-induced local structural changes. Since no distinct PL peak shift was observed after the laser irradiation at low temperatures, photoexcitation is a useful technique to improve the luminescence efficiency only.

Photoemission spectroscopy and in-situ spectroscopic ellipsometry studies on the Ar post-oxidation-annealing effects of oxide/SiC interfaces
,Proceedings of 1st Asia-Pacific Workshop on Widegap Semiconductors:127-132 2003
Y. Hijikata, S. Kawato, S. Sekiguchi, H. Yaguchi, Y. Ishida, M. Yoshiawa, T. Kamiya and S. Yoshida
The effect of post-oxidation annealing in Ar atmosphere (Ar-POA) on 4H-SiC/oxide interfaces has been studied by photoemission and ellipsometry measurements, It was shown by angle-resolved x-ray photoelectron spectroscopy (AR-XPS) and ultraviolet photoelectron spectroscopy (UPS) measurements that the concentration of Si3+ and C-C bond and the structures of O2p twin peaks changed remarkably around 600C. It was also found from the in-situ spectroscopic ellipsometry studies that there exist interface layers having higher refractive index than those of stoichiometric SiO2 and SiC and the refractive indices of the interface layers also decreases by Ar-POA at the temperatures above 600C. It has been reported by C-V measurements on SiC metal-oxide-semiconductor (MOS) capacitors that the magnitude of flat-band shift decreases by Ar-POA around the same temperature as that observed by photoelectron and optical measurements mentioned above. These results suggest that the structural changes at the interfaces observed by ohotoemission spectroscopy and ellipsometry are the origins that bring about the flat-band voltage shift in C-V properties by Ar-POA.

Spectroscopic ellipsometry study on the dielectric functions of GaPN alloys
,Physica Status Solidi (b)(7):2753-2756 2003
H. Kanaya, H. Yaguchi, Y. Hijikata, S. Yoshida, S. Miyoshi, and K. Onabe
We have determined the complex dielectric functions of GaP1-xNx alloys using spectroscopic ellipsometry to clarify the electronic structure. With increasing N concentration, the E1-gap peak height for both e1 and e2 decreases and the E1-gap energy shifts to higher energies, showing that the electronic state at the L point is considerably changed due to the N incorporation. In the lower energy range, a broad peak appears near the fundamental band gap energy of GaP. With increasing N concentration, this peak becomes broader and the peak height increases. This indicates that the band-edge formation in GaP1-xNx alloys is extremely unique compared to that in conventional semiconductor alloys.

Characterization of the Interfaces between SiC and Oxide Films by Spectroscopic Ellipsometry
,Materials Science Forum,389-393:1029-1032 2002
Y. Tomioka, T. Iida, M. Midorikawa, H. Tukada, K. Yoshimoto, Y. Hijikata, H. Yaguchi, M. Yoshikawa, Y. Ishida, R. Kosugi and S. Yoshida
Spectroscopic ellipsometry has been used to investigate, for the first time, the optical properties of oxide films on SiC to discuss the difference of the structure of SiC/SiO2 interfaces with oxidation processes, thermal oxidation in dry oxygen, pyrogenic oxidation and low temperature deposition of oxides by chemical vapor deposition. It was found that there exist interface layers with high refractive indices between SiC and SiP2, the values of which are larger than those of SiC and SiO2 and depend on the oxidation process. The validity of the evaluation of refractive indices of the interfaces has also been discussed.
6H-SiC, Optical Constant, Oxidation, Refractive Index, SiO2/SiC Interface, Spectroscopic Ellipsometry (SE)

Control of Macroscopic Absorption Coefficient of Multicrystalline SiGe by Microscopic Compositional Distribution
,Japanese Journal of Applied Physics,41(1A/B):L37-L39 2002
N. Usami, K. Fujiwara, T. Ujihara, G. Sazaki, H. Yaguchi, Y. Murakami and K. Nakajima
We report on the growth and optical characterizations of multicrystalline SiGe (mc-SiGe) with microscopic compositional distribution for solar cell applications. Mc-SiGe was grown by a simple technique based on the casting method. The compositional distribution and solidification structure of mc-SiGe were found to be strongly dependent of the cooling rate, suggesting that they can be controlled by the growth parameters. Spatial variation of the extinction coefficient, corresponding to the microscopic compositional distribution, was revealed by spectroscopic ellipsometry, and macroscopic optical properties were found to be controlled by the microscopic compositional distribution. The advantage of mc-SiGe was further revealed by the increased absorption in the lower energies compared with uniform SiGe with almost the same average composition.
multicrystalline SiGe, microscopic compositional distribution, solar cells

Measurements of the Depth Profile of the Refractive Indices in Oxide Films on SiC by Spectroscopic Ellipsometry
,Japanese Journal of Applied Physics,41(2A):800-804 2002
T. Iida, Y. Tomioka, K. Yoshimoto, M. Midorikawa, H. Tukada, M. Orihara, Y. Hijikata, H. Yaguchi, M. Yoshikawa, H. Itoh, Y. Ishida and S. Yoshida
The depth profiles of the refractive indices in thermally oxidized films on SiC have been measured by spectroscopic ellipsometry. Oxide films etched at an angle were used to obtain the depth profiles of the refractive indices in the oxide films. The apparent refractive indices napp and thicknesses have been evaluated, assuming that the films have optically uniform single layer structures. The experimental results show that the values of napp increase with oxide film thickness, and approach the values for oxide films on Si at around 60 nm in thickness. This feature is almost the same as the changes of refractive indices of oxide films with oxidation time reported previously. These results reveal that the oxide films are not optically uniform and that the optical properties change with depth from the surface. It has been found that the film structure model where the oxide film is composed of two layers, a thin interface layer around 1 nm in thickness with a higher refractive index than those of SiC and SiO2 and a stoichiometric SiO2 layer, the thickness of which changes with film thickness, can explain the thickness dependence of napp observed. These results suggest that there exists an interface layer with high refractive indices at oxide film/SiC interfaces.
spectroscopic ellipsometry, 6H-SiC, refractive indices, oxide films, SiC/SiO2 interface

Spatial Mapping of the Carrier Concentration and Mobility in SiC Wafers by Micro Fourier-Transform Infrared Spectroscopy
,Materials Science Forum,389-393:621-624 2002
H. Yaguchi, K. Narita, Y. Hijikata, S. Yoshida, S. Nakashima and N. Oyanagi
Micro Fourier-transform infrared (FTIR) spectroscopy has been used to investigate the spatial distribution of the carrier concentration and mobility in SiC wafers. The carrier concentration and mobility were independently derived from the reflectance spectra based on the dielectric function taking into account the effect of phonons and plasmons. The carrier concentration profile obtained for an intentionally inhomogeneous N-doped 6H-SiC wafer coincides well with the spatial distribution of color in the wafer. For commercially available wafers, carrier concentrations are found to increase with approaching the center of the wafers. These results demonstrate that micro FTIR is a nondestructive and noncontact technique to spatially characterize the carrier concentration and mobility in SiC wafers.

X-Ray Photoelectron Spectroscopy Studies of Post-Oxidation Process Effects on Oxide/SiC Interfaces
,Materials Science Forum,389-393:1033-1036 2002
Y. Hijikata, H. Yaguchi, M. Yoshikawa and S. Yoshida
In this report, we carried out x-ray photoelectron spectroscopy measurements on slope shaped oxide films to explore the changes of interfacial structures by post oxidation processes. By the observation of Si2p, C1s and O1s spectra, the bonding states which influence the electrical properties of MOS structures were suggested to be bonds related to carbon. We also discuss the reasons for the improvement of MOS properties by these post oxidation processes.
Bond, Post-Oxidation Annealing, Re-Oxidation, SiC MOSFET, Slope-Shaped Oxide Film, X-Ray Photoelectron Spectroscopy (XPS)

Composition Analysis of SiO2/SiC Interfaces by Electron Spectroscopic Measurements Using Slope Shaped Oxide Films
,Applied Surface Science,184(1-4):161-166 2001
Y. Hijikata, H. Yaguchi, M. Yoshikawa and S. Yoshida
We have characterized SiO2/SiC interfaces by X-ray photoelectron spectroscopy in terms of composition and bonds to clarify the reasons for the problems in silicon carbide metal-oxide-semiconductor field-effect-transistor and MOS structures. The oxide films on 6H-SiC were shaped into slopes by HF chemical etching to obtain the depth profile of the composition and the bondings. An interface layer was found near the SiO2/SiC boundary, where SiO2 stoichiometry is collapsed and there exists the bondings other than Si-O2 and Si-C. Also, we revealed the differences in the interface properties for different oxidation processes.
6H–SiC, Oxidation, Slope-shaped oxide film, SiO2/SiC interface, XPS, Bonding

Photoluminescence Study on Temperature Dependence of Band Gap Energy of GaAsN Alloys
,Physica Status Solidi (b),228(1):273-277 2001
H. Yaguchi, S. Kikuchi, Y. Hijikata, S. Yoshida, D. Aoki and K. Onabe
We have studied the temperature dependence of photoluminescence (PL)spectra of GaAsN alloys. The PL peak energy shift due to the temperature change decreases with increasing N concentration of GaAsN alloys. The localized state emission partly contributes to the decrease in the PL peak energy shift.In addition, the small PL peak energy shift at high temperatures is due to the reduction in the temperature dependence of the band gap energy. From the analysis using the Bose-Einstein statistical expression, the average phonon energy is much larger than that expected from the linear interpolation between GaAs and GaN, indicating that the interaction between electrons and phonons localized at N atoms plays an important role in the reduction of the temperature dependence of the band gap energy of GaAsN alloys.

Spectroscopic Ellipsometry Study on the Electronic Structure near the Absorption Edge of GaAsN Alloys
,Physica Status Solidi (b),228(1):269-272 2001
H. Yaguchi, S. Matsumoto, Y. Hijikata, S. Yoshida, T. Maeda, M. Ogura, D. Aoki and K. Onabe
Spectroscopic ellipsometry has been used to investigate the electronic structure near the fundamental absorption edge of GaAsN alloys grown by metalorganic vapor phase epitaxy.The fundamental absorption edge is clearly observed in the imaginary part of the dielectric function and shifts to lower energies with increasing N concentration.In addition,the absorption structure is observed near the E0 gap energy of GaAs even in GaAsN alloys.This unequivocally shows that the fundamental absorption edge of GaAsN is not shifted from the E0 gap of GaAs but newly formed by the N incorporation.Thus,the formation of the narrowest band gap of GaAsN alloys is found to be completely different from that of conventional compound semiconductor alloys,such as AlGaAs and GaAsP.

Temperature Dependence of Excitonic Gammac-Gammav Transition Energies of GaxIn1-xP Crystals
,Japanese Journal of Applied Physics,40:1183-1187 2001
Y. Ishitani, H. Yaguchi and Y. Shiraki
The excitonic Gammac-Gammav transition energies of disordered GaxIn1-xP (x = 0.0, 0.52, 0.70, and 1.0) crystals have been measured by photoreflectance (PR) measurements at temperatures from 20 to 300 K. The photoluminescence (PL) peak energy at 20 K is found to be lower than the energy obtained from PR or photoluminescence excitation (PLE) spectra by about 6 meV. The temperature dependence of the transition energy is expressed by a function consisting of several terms, each of which represents the effect of the volume-thermal expansion of the electron-phonon interaction. It is found that the temperature-dependent decrease of the transition energy from the pure electronic transition energy is mainly caused by the electron-phonon interaction. The energy shift due to the electron-phonon interaction increases as the GaP mole fraction increases.
excitonic Γc–Γv transition energy, photoreflectance, electron-phonon interaction, volume-thermal expansion effect, GaxIn1-xP crystal

Characterization of Oxide Films on SiC by Spectroscopic Ellipsometry
,Japanese Journal of Applied Physics,39(10B):L1054-L1056 2000
T. Iida, Y. Tomioka, Y. Hijikata, H. Yaguchi, M. Yoshikawa, Y. Ishida, H. Okumura and S. Yoshida
We have, for the first time, evaluated the optical constants of thermally oxidized films on SiC by spectroscopic ellipsometry, and discussed the characteristics of SiC/SiO2 interfaces. It was found that the effective refractive indices are smaller than those of the oxide films on Si. They increase with oxidation time, or oxide thickness, reaching to the values of Si oxides. The refractive indices also depend on the oxidation methods, and the pyrogenic oxidation brings about larger refractive indices than dry oxidation. The origin of the small refractive indices of oxide films on SiC was discussed in terms of interface structures and composition in comparison with those of oxide films on Si.
spectroscopic ellipsometry, 6H-SiC, refractive index, oxidation, SiC/SiO2 interface

Fabrication and optical properties of GaAs/AlGaAs quantum dot grown in tetrahedral-shaped recesses on GaAs (111) B substrates by MOVPE
,Physica E,7(3):308-316 2000
T. Tsujikawa, S. Mori, H. Watanabe, M. Yoshita, H. Akiyama, R. van Dalen, K. Onabe, H. Yaguchi, Y. Shiraki and R. Ito
GaAs/AlGaAs quantum dots were grown in tetrahedral-shaped recesses (TSRs) on GaAs(-1-1-1)B substrates at 850 degrees C by metalorganic vapor-phase epitaxy on the bottom (-1-1-1)B regions of the TSRs. As the AlGaAs barrier layer became thicker, a trench-like region comprised of {11-2} and {-1-12} vertical sidewalls formed at the bottom region of the TSR. A 780 \AA-wide and 96 \AA-thick GaAs quantum dot was formed at the bottom of the trench-like region. The luminescence from GaAs layer at only the (-1-1-1)B bottom region of the TSR was confirmed by cathodoluminescence image observation. By micro-photoluminescence observation a narrow line from the bottom region was observed at 1.5511 eV and the luminescence from higher-energy states was observed. The calculation for a 780 \AA * 780 \AA * 96 \AA quantum box revealed that these energy states reflected both the lateral and vertical quantum confinements.

Optical characterization of metalorganic vapor-phase epitaxy-grown GaAs1-xNx alloys using spectroscopic ellipsometry
,Journal of Crystal Growth,221(1-4):481-484 2000
S. Matsumoto, H. Yaguchi , S. Kashiwase, T. Hashimoto, S. Yoshida, D. Aoki and K. Onabe
We have measured complex dielectric functions, epsilon1+i epsilon2, of GaAs1-xNx alloys using spectroscopic ellipsometry to investigate higher-energy band gaps. The E1 gap-related peak height for epsilon2 decreases with increasing N concentration, indicating that the optical absorption at the E1 gap decreases. On the contrary, the E2 gap transition does not change so much with varying N concentration. These results are consistent with the theoretical study, which predicts that the lowest conduction band is mostly a combination of the Gamma and L states. The bowing parameters of the E1 and E2 gaps are rather large but much smaller than the bowing parameter of the E0 gap.
GaAsN, Complex dielectric functions, Spectroscopic ellipsometry, Band gap bowing

Optical Constants of Cubic GaN, AlN and AlGaN Alloys
,Japanese Journal of Applied Physics,39(6A):L497-L499 2000
T. Suzuki, H. Yaguchi, H. Okumura, Y. Ishida and S. Yoshida
We have used spectroscopic ellipsometry to investigate, for the first time, the optical constants of cubic GaN, AlN, and AlGaN alloy epitaxial layers grown by molecular beam epitaxy. The refractive indices of cubic AlGaN were found to decrease with increasing Al content, as expected from the empirical observation that the refractive index decreases with increasing direct bandgap energy. In the transparent wavelength region, the refractive indices of cubic AlGaN with lower Al contents are somewhat larger than those of hexagonal modifications, while with higher Al contents, the refractive indices of cubic AlGaN and hexagonal AlGaN are almost equal. We also found that the direct bandgap energies of cubic AlGaN show a parabolic dependence on the Al content.
spectroscopic ellipsometry, cubic GaN, cubic AlN, cubic AlGaN, optical constants, direct bandgap energy

Optical properties of cubic GaN grown on 3C-SiC (100) substrates by metalorganic vapor phase epitaxy
,Physica Status Solidi (a),180(1):403-407 2000
J. Wu, H. Yaguchi, B.P. Zhang, Y. Segawa, K. Onabe and Y. Shiraki
Cubic GaN with different low-temperature buffer layers were grown on 3C-SiC (100) substrates by metalorganic vapor phase epitaxy (MOVPE). The sample surface morphology was affected considerably by the thickness of the buffer layer. An X-ray diffraction-peak shift was observed for these samples, indicating the existence of residual strain inside the crystal. The origin of the residual strain can be attributed to the different thermal expansion coefficients of GaN and 3C-SiC. The residual strain has a strong influence on the excitonic transition energies. From the strain dependence of the shift of the exciton peaks, the value of the excitonic bandgap and the strain coefficient (relation between strain parallel to z-axis and exciton energy) of cubic GaN were estimated.

Second-Harmonic Generation from GaP/AlP Multilayers on GaP (111) Substrates Based on Quasi-Phase Matching for the Fundamental Standing Wave
,Japanese Journal of Applied Physics,39(4B):L334-L336 2000
M. Sato, H. Yaguchi, I. Shoji, K. Onabe, R. Ito, Y. Shiraki, S. Nakagawa and N. Yamada
We have demonstrated second-harmonic generation (SHG) from GaP/AlP multilayers on GaP(111)A substrates based on quasi-phase matching (QPM) for the fundamental standing wave. Theoretical calculation predicted that the SHG power increases with increasing number of GaP/AlP multilayers because of their small absorption coefficient in the spectral rage of second-harmonic light, which is in contrast to the case of GaAs/AlAs QPM multilayres. In the transmission SHG measurements using a frequency-tunable Ti:Sapphire laser as a fundamental wave source, maximum SHG power was obtained at a fundamental wavelength of 990 nm from the five-pair GaP/AlP QPM multilayres. The wavelength conversion efficiency was measured to be 9.8*10-10%/W, which was smaller than the theoretical value of 6.5*10-8%/W.
SHG, QPM multilayers, GaP, AlP, (111)A, MOVPE, conversion efficiency

High-Temperature Metalorganic Vapor Phase Epitaxial Growth of GaAs/AlGaAs Quantum Structures in Tetrahedral-Shaped Recesses on GaAs (111)B Substrates
,Japanese Journal of Applied Physics,38(1B):459-464 1999
T. Tsujikawa, T. Irisawa, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito
GaAs/AlGaAs quantum structures were grown in tetrahedral-shaped recesses (TSRs) on GaAs (111)B substrates at temperatures above 800 degrees C by metalorganic vapor phase epitaxy because quantum dots were expected to be formed at the bottom (111) regions of the TSRs. Observation of cathodoluminescence revealed that GaAs quantum structures with different layer thicknesses were formed at (100) edge regions, (110) and (111)A sidewalls and the (111) bottom and surface regions of the TSR. Growth on the (111)B surface region between TSRs was clearly observed for the sample grown at 850 degrees C. As the growth temperature was raised above 850 degrees C, the photoluminescence intensity on the (111)B surface increased whereas that on the (001) edge regions and (111)A sidewall regions decreased. With an increase in well thickness, the luminescence from the bottom and edge regions was simultaneously observed. A 50 AA-thick quantum well was formed on the small bottom region. From scanning electron microscope observation, the lateral size of the region was 550 AA.
quantum dot, tetrahedral-shaped recesses, cathodoluminescence, GaAs, AlGaAs, metalorganic vapor phase epitaxy

MOVPE Growth and Luminescence Properties of GaAsN Alloys with Higher Nitrogen Concentrations
,Physica Status Solidi (a),176(1):231-235 1999
K. Onabe, D. Aoki, J. Wu, H. Yaguchi and Y. Shiraki
Highly luminescent GaAsN alloy films have been successfully obtained with N concentrations up to 3.1% by metalorganic vapor phase epitaxy (MOVPE). The band-gap bowing parameter estimated from the photoluminescence (PL) peak energy is not constant but dependent on the N concentration; 24.0 eV for N<1% and 17.0 eV for N>1% at 20 K, and 22.4 eV for N<1% and 14.5 eV for N>1% at room temperature. From the characteristic features of the luminescence properties, the band-edge states are found to be much localized below the conduction band edge, and the emission process at low temperatures is associated with these localized states as in GaPN alloys.

Optical characterization of cubic AlGaN epilayers by cathodoluminescence and spectroscopic ellipsometry
,Physica Status Solidi (b),216(1):211-214 1999
H. Okumura, T. Koizumi, Y. Ishida, H. Yaguchi and S. Yoshida
Cubic AlGaN epilayers grown by molecular beam epitaxy were characterized by cathodoluminescence and spectroscopic ellipsometry techniques. The linear increase of the bandgap energy versus Al composition was consistently confirmed by the two techniques, which indicate the direct transition nature of cubic AlGaN band structure. The energy dependence of optical constants for cubic GaN was also obtained by the simulation of the measured ellipsometric data.

Photoluminescence study of InP/GaP highly strained quantum wells
,Institute of Physics Conference Series,162:511-516 1999
T. Kimura, H. Yaguchi, N. Usami, K. Onabe and Y. Shiraki
InP/GaP highly strained quantum wells (QWs) grown by metalorganic vapor phase epitaxy (MOVPE) are studied by photoluminescence (PL) spectroscopy. Four sharp and intense peaks from the InP/GaP highly strained QWs are clearly observed at 5 K. Considering the energy differences between the peaks, these are assigned as the no-phonon (NP) emission, TAx, LAx, and TOx phonon replicas. This shows that the optical transition of the InP/GaP highly strained QW is indirect under the compressive strain. Using a combination of PL and atomic force microscopy, it is found that the wetting layer continuously grows even after the InP island formation begins. Moreover, a calculation indicates that the thickness of the wetting layer finally approaches ~2 ML.

Quantum size effect of lead iodide nanoparticles formed by a Langmuir-Blodgett technique
,Mol. Cryst. Liq. Cryst,337:225-228 1999
T. Yamaki, K. Asai, K. Ishigure, K. Ema and H. Yaguchi
Nanoparticles of lead iodide (PbI2) were prepared by exposure of Langmuir-Blodgett (LB) films of lead arachidate to hydrogen iodide. The photoluminescence (PL) spectrum of the nanoparticles consisted of three bands: an exciton band and two low-energy bands associated with stoichiometric and structural defects. The center of the exciton band was blue-shifted due to a quantum size effect. The PL spectra drastically changed when the temperature increased.

Selective Growth of Cubic GaN on Patterned GaAs (100) Substrates by Metalorganic Vapor Phase Epitaxy
,Physica Status Solidi (a),176(1):557-560 1999
J. Wu, M. Kudo, A. Nagayama, H. Yaguchi, K. Onabe and Y. Shiraki
Selective growth of cubic GaN on patterned GaAs substrates was studies. The structural and morphological properties of cubic GaN are very dependent on the orientation of the mask stripes. In the case of window stripe opening along [011] direction, (111)B facets were clearly observed in all the samples, regardless of the different growth time. Both X-ray diffraction and photoluminescene measurements showed that the hexagonal GaN os easily constructed along the (111)B facet. In contrast, window stripes opening along [01-1] direction resulted in the formation of (311)A facets and subsequently a relatively flat surfaces occurred as the growth proceeded. Strong emission peaks of cubic GaN were observed in the photoluminescence spectra.

Stimulated emission from optically pumped cubic GaN/AlGaN double heterostructures
,Journal of Crystal Growth,197(1-2):73-77 1999
J. Wu, H. Yaguchi, K. Onabe and Y. Shiraki
Cubic GaN/AlGaN heterostructures were grown on semi-insulating GaAs(100) substrates by metalorganic vapor-phase epitaxy. Optical pumping experiments were performed on cubic GaN/AlGaN cavities, which were formed simply by cleaving the substrate. Strong stimulated emission at a wavelength of 394 nm was observed from the cleaved edge of the optically pumped cubic GaN/AlGaN heterostructures at 15 K. The stimulated emission was demonstrated by the superlinear increase of the output intensity and the highly TE-polarized nature. Besides this strong stimulated emission, an additional stimulated emission centered at 383 nm is also observed from some samples.
Stimulated emission, MOVPE, Cubic GaN, Cubic AlGaN, Heterostructures, Cleaved cavity

Substrate misorientation dependence of the hexagonal phase inclusion in cubic GaN films grown by metalorganic vapor phase epitaxy
,Physica Status Solidi (a),176(1):513-517 1999
A. Nagayama, R. Katayama, N. Nakadan, K. Miwa, H. Yaguchi, J. Wu, K. Onabe and Y. Shiraki
The metalorganic vapor phase epitaxial (MOVPE) growth of cubic GaN layers on misoriented GaAs (001) substrates, the faces of which were tilted from (001) toward [110] or [110] by 4 degrees , was performed in order to investigate the effect of the substrate misorientation on the inclusion of hexagonal phase in the cubic GaN layer. The sample grown on the tilted surface toward [110] showed an enhanced generation of the hexagonal domain on the (111) face, whereas the hexagonal domain on the (111) face was suppressed. The sample grown on the tilted surface toward [110] showed the generation of the hexagonal domains on both the (111) and (111) faces with an equal magnitude. It is suggested that the generation of hexagonal domains may be suppressed when the exposure of the (111) or (111) faces by the thermal damage of the substrate surface is reduced.

Time-Resolved Photoluminescence of Cubic GaN Grown by Metalorganic Vapor Phase Epitaxy
,Physica Status Solidi (b),216(1):237-240 1999
H. Yaguchi, J. Wu, H. Akiyama, M. Baba, K. Onabe and Y. Shiraki
Time-resolved photoluminescence of high quality cubic GaN was measured to clarify the origin of the emissions observed in cubic GaN. The 3.27 eV emission decay was fast and the intensity decreased with a lifetime of 260 ps at early decay and with a lifetime of 900 ps afterwards. The decay of the 3.18 eV emission was much slower than that of the 3.27 eV emission and the lifetime was 3.8 ns. In time-resolved spectra, the 3.18 eV emission had a broadening on the high-energy side at early times and the peak moved to lower energies with increasing time. These results can be explained in terms of the model for a donor-acceptor pair transition.

A New Approach to ZnCdSe Quantum Dots
,Materials Science & Engineering B,51(1-3):127-131 1998
B.P. Zhang, T. Yasuda, W.X. Wang, Y. Segawa, K. Edamatsu, T. Itoh, H. Yaguchi and K. Onabe
We propose a new approach of fabricating ZnCdSe quantum dots (QDs) on ZnSe and GaAs (110) surfaces by simply depositing a ZnSe/ZnCdSe/ZnSe heterostructure. The growth conditions are selected to introduce surface roughness on the over grown ZnSe which allows the formation of ZnCdSe QDs. Optical studies unambiguously demonstrate the formation of QDs. Resolution-limited sharp emission lines are observed by micro-photoluminescences and the linewidths are much less than the thermal energy. As time goes on, intermittent behaviors of the QD emissions are observed. A proper selection of growth conditions is essential in obtaining ZnCdSe QDs by this method, especially on GaAs (110) surfaces.
ZnCdSe, Quantum dot, Micro-photoluminescence

Characterization of SiGe Strained Heterostructure Grown by Molecular Beam Epitaxy Using a Si Effusion Cell
,Thin Solid Films,321(1-2):241-244 1998
H. Yaguchi, T. Yamamoto and Y. Shiraki
We characterize SiGe strained heterostructures grown by molecular beam epitaxy (MBE) using a Si effusion cell which can be used at high temperatures up to 1700 degrees C instead of an electron beam gun conventionally used in solid-source Si MBE. Photoluminescence is clearly observed from a Si/SiGe quantum well grown on a Si(001) substrate using the Si effusion cell. This indicates that the sample grown with the Si effusion cell is of good quality. It is found from X-ray diffraction measurement of a Ge/Si strained-layer superlattice grown on a Ge(001) substrate that good controllability of the growth rate can be realized by using the Si effusion cell. Optical transitions observed in the photoreflectance spectrum of the Ge/Si strained layer superlattice agree with the Kronig-Penny model calculation taking account of the non-parabolicity of the conduction band.

Cleaved cavity stimulated emission from an optically pumped cubic GaN/AlGaN heterostructure grown on GaAs (100) substrate
,Applied Physics Letters,73(14):1931-1933 1998
J. Wu, H. Yaguchi, K. Onabe and Y. Shiraki
Cubic GaN/AlGaN double heterostructure was grown on semi-insulating GaAs (100) substrate by metalorganic vapor phase epitaxy. Strong stimulated emission was observed from the cleaved edge of the optically pumped cubic GaN/AlGaN heterostructure at 15 K. The cavity was formed simply by cleaving the substrate. The stimulated emission was demonstrated by the superlinear increase of the output intensity and the highly transverse electric polarized nature. The stimulated emission showed an obvious redshift compared with the spontaneous one.

Exciton diffusion dynamics in quantum nanostructures on V-groove patterned substrates
,Superlattices and Microstructures,23(2):395-400 1998
N. Usami, Y. Shiraki, W. Pan, H. Yaguchi and K. Onabe
Time-resolved photoluminescence (PL) measurements were performed for two different quantum nanostructures on V-groove patterned substrates; SiGe/Si quantum wells (QWs) on V-grooved Si substrates and AlGaAs spontaneous vertical quantum wells on V-grooved GaAs substrates. Anomalous behaviours of the PL, such as the decrease of the decay time of the SiGe (111) QWs and the (111)A AlGaAs layer, were fully explained by taking the exciton diffusion towards the bottom of the V-groove into account, showing that the exciton diffusion driven by the spatial nonuniformity of the alloy compositions and/or geometry of the substrates is a key to controlling the PL properties of the nanostructures.

Fabrication of Pb(Zr,Ti)O3/MgO/GaN/GaAs structure for optoelectronic device applications
,Journal of Crystal Growth,189/190:227-230 1998
A. Masuda, S. Morita, H. Shigeno, A. Morimoto, T. Shimizu, J. Wu, H. Yaguchi and K. Onabe
Pb(Zr,Ti)O3 (PZT) films were deposited on cubic GaN/(100)GaAs for the first time with or without MgO buffer layer by pulsed laser ablation. MgO films were grown on cubic GaN with cube-on-cube epitaxy. It was found that MgO buffer layer is very useful for suppressing the diffusion of O and metal elements into GaN layer. Preferentially [100]-oriented perovskite PZT films were obtained on cubic GaN with MgO buffer layer although randomly oriented perovskite PZT films were obtained without MgO buffer layer. PZT/MgO/GaN structure is one of the promising candidates for integrated devices composed of ferroelectric waveguides and blue laser diodes.
Cubic GaN, Pb(Zr,Ti)O3 (PZT), MgO buffer layer, Ferroelectric waveguide, Pulsed laser ablation (PLA), Pulsed laser deposition (PLD)

GaAs/AlGaAs Quantum Structures Grown in Tetrahedral-Shaped Recesses on GaAs(111)B Substrates by Metalorganic Vapor Phase Epitaxy
,Japanese Journal of Applied Physics,37(3B):1493-1496 1998
T. Tsujikawa, K. Momma, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito
GaAs/AlGaAs quantum structures were grown in tetrahedral-shaped recesses (TSRs) on GaAs (111)B substrates at different growth rates by metalorganic vapor phase epitaxy. Observation of cathodoluminescence revealed that GaAs quantum structures with different layer thicknesses were formed at {100} edge regions, {110} and {111} A sidewalls and the {111} bottom region of the TSR. The luminescence from the bottom region of the TSRs was clearly seen in the sample grown at a large growth rate. With increasing growth rate, the thickness in the bottom region increased, whereas the thickness at the edge regions decreased. This is explained by a reduction in the migration distance of Ga adatoms from the {111} bottom region to the other regions.
quantum dot, tetrahedral-shaped recesses, cathodoluminescence, migration distance, GaAs, AlGaAs, metalorganic vapor phase epitaxy

Investigation of luminescence properties of GaN single crystals grown on 3C-SiC substrates
,Journal of Crystal Growth,189/190:420-424 1998
J. Wu, H. Yaguchi, H. Nagasawa, Y. Yamaguchi, K. Onabe, Y. Shiraki and R. Ito
Cathodoluminescence (CL) and photoluminescence (PL) investigations of single crystal GaN grown on 3C-SiC(100) substrates by metalorganic vapor-phase epitaxy are reported. The GaN grown on 3C-SiC substrates shows distinct crystal facets. We identified the square facet and inclined facet as cubic GaN and hexagonal GaN, respectively. We studied the luminescence properties from the square facet or from the inclined facets separately by CL. For the cubic GaN, a sharp excitonic transition and a weak DA pair transition were observed from the square facet. On the other hand, an emission line at 3.293 eV was obtained from the inclined facets. By studying its temperature dependence, we suggest that the 3.293 eV emission is due to the free electron to acceptor transition of hexagonal GaN.
Cubic GaN, Hexagonal GaN, MOVPE, Cathodoluminescence, Photoluminescence

Metalorganic vapor phase epitaxy growth and photoluminescence properties of cubic AlxGa1-xN
,Applied Physics Letters,73(2):193-195 1998
J. Wu, H. Yaguchi, K. Onabe and Y. Shiraki
We have grown cubic AlxGa1-xN (0<x<0.25) films on GaAs (100) substrates by metalorganic vapor phase epitaxy. A strong excitonic transition, as well as a donor-acceptor pair transition and a deep-level emission, was observed in the photoluminescence spectra at 5 K in all the samples. With increasing Al fraction, all the emission lines shift to higher energy, nevertheless, with different shift rates. The temperature-dependent photoluminescence spectra show that the behavior of the donor-acceptor pair transition varied with Al fraction; at higher Al concentrations, the donor-acceptor pair transition tends to transform to a free-electron to acceptor transition and survive even at room temperature. This can also explain the energy shift to higher energy with increasing temperature for this emission line.

Metalorganic Vapor Phase Epitaxy Growth of High Quality Cubic GaN on GaAs(100) Substrates
,Japanese Journal of Applied Physics,37(3B):1440-1442 1998
J. Wu, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito
We report on the growth of high quality cubic GaN films on GaAs (100) substrates by low pressure metalorganic vapor phase epitaxy. The GaN films exhibit a smooth surface which is free from cracks. X-ray diffraction shows the cubic nature of the GaN films. X-ray rocking curve with omega scan shows that the crystal quality of GaN films improves markedly with increasing growth temperatures. Photoluminescence measurements confirm the high quality of the cubic GaN films. The full width at half maximum of excitonic emission from the cubic GaN films is as narrow as 70 meV at 300 K.
MOVPE, cubic GaN, high quality, 1,1-dimethylhydrazine (DMHy), X-ray diffraction, photoluminescence

Metalorganic Vapor Phase Epitaxy of High Quality Cubic GaN,AlGaN and Their Application to Optical Devices
,Proceeding of the 2nd International Symposium on Blue Laser and Light Emitting Diodes:715-718 1998
J. Wu, H. Yaguchi, K. Onabe and Y. Shiraki
We report on the growth of cubic GaN and AlGaN on GaAs (100) substrates by metalorganic vapor phase epitaxy (MOVPE). High optical quality cubic nitrides were obtained by optimizing the growth conditions. X-ray diffraction measurements confirmed the highly cubic nature of these films. Photoluminescence spectra showed dominant excitonic transition for both cubic GaN and AlGaN. Strong stimulated emission was observed from the cleaved edge of optically pumped cubic GaN/AlGaN double hetero (DH) structures.

Metalorganic vapor-phase epitaxy of GaP1-x-yAsyNx quaternary alloys on GaP
,Journal of Crystal Growth,189/190:485-489 1998
G. Biwa, H. Yaguchi, K. Onabe and Y. Shiraki
We report on a successful growth of GaP1-x-yAsyNx quaternary alloys on GaP by metalorganic vapor-phase epitaxy (MOVPE). The arsenic solid composition increases with increasing AsH3 supply during the MOVPE growth, while the nitrogen composition is unchanged. The alloys with compositions (x~2.3%, 0<y<19%) are obtained, and the control of the lattice constant in GaP1-x-yAsyNx quaternary alloys is demonstrated. From the dependence of photoluminescence (PL) intensities on lattice mismatch to GaP substrates, we found that lattice-matching to substrates is necessary to obtain GaP1-x-yAsyNx alloys with high quality and intense PL.
GaPAsN, GaPN, Metalorganic vapor-phase epitaxy (MOVPE), Nitride alloy, Metastable alloy, Lattice match

Micro Raman and micro photoluminescence study of cubic GaN grown on 3C-SiC(001) substrates by metalorganic vapor phase epitaxy
,Journal of Crystal Growth,195(1-4):323-327 1998
H. Yaguchi, J. Wu, B. Zhang, Y. Segawa, H. Nagasawa, K. Onabe and Y. Shiraki
We have investigated metalorganic vapor phase epitaxy-grown GaN grains on a 3C-SiC(001) substrate using micro Raman and micro photoluminescence spectroscopy. Polarized micro Raman spectra clearly showed that horizontal flat facets and inclined facets of the rectangular GaN grains correspond to cubic phase regions and hexagonal phase regions, respectively. To examine the photoluminescence properties of "pure" cubic GaN, micro photoluminescence was performed by focusing a laser beam on the horizontal flat facet. A strong photoluminescence line with the full-width at half-maximum of 5 meV was observed, which is the smallest value to date and shows that the crystal quality of the cubic phase region is excellent. We could clearly identify free exciton, donor bound exciton and acceptor bound exciton emissions in the cubic GaN.

Molecular beam epitaxy of SiGe heterostructures using a newly designed Si effusion cell
,Materials Science & Engineering B,51(1-3):170-172 1998
H. Yaguchi, T. Yamamoto and Y. Shiraki
We demonstrate the usefulness of a newly designed Si effusion cell which can be used at high temperatures up to 1700 degrees C instead of a conventional electron beam evaporator in solid-source Si molecular beam epitaxy. The growth rate ranges from 0.005 to 0.5 AA/s at temperatures from 1350 to 1650 degrees C and agrees well with the temperature dependence of the Si vapor pressure. Photoluminescence was observed from a Si/SiGe quantum well grown on a Si substrate using the Si effusion cell. This indicates that the sample has little defects or dislocations which may result in nonradiative recombination centers or deep levels. It is found from photoreflectance and X-ray diffraction measurements that excellent controllability of the growth rate can be realized by using the Si effusion cell.
Molecular beam epitaxy, Si effusion cell, SiGe, Heterostructure

MOVPE growth of GaPAsN quaternary alloys lattice-matched to GaP
,Materials Research Society Symposium Proceeding,482:173-178 1998
G. Biwa, H. Yaguchi, K. Onabe and Y. Shiraki
GaP1-x-yAsyNx (x~2.3%, 0<y<19%) quaternary alloy semiconductor films on GaP substrates have been successfully grown by metalorganic vapor phase epitaxy (MOVPE). With the fixed supplies of trimethylgallium (TMG), AsH3 and dimethylhydrazine (DMHy) during the growth, the As concentration in the solid increased with increasing AsH3 supply, while the N concentration was almost unaffected. It has been demonstrated that the crystalline quality of the alloy films is much improved with the close lattice matching to the GaP substrate, giving a superior surface morphology without any cross-hatches, a much narrower X-ray diffraction linewidth, and a significantly higher photoluminescence (PL) intensity.

Optical transitions in cubic GaN grown on GaAs(100) substrates by metalorganic vapor-phase epitaxy
,Journal of Crystal Growth,189/190:415-419 1998
J. Wu, H. Yaguchi, K. Onabe, R. Ito and Y. Shiraki
We investigated the optical transitions in cubic GaN films grown on GaAs(100) substrates by metalorganic vapor-phase epitaxy. The cubic GaN films show good optical quality. From temperature and excitation intensity dependence, the emission lines at 3.274 and 3.178 eV were assigned to the excitonic transition and the donor-acceptor pair transition, respectively. We also suggested an additional acceptor level (EA' equivalent to 212 meV) to explain the origin of the emission lines at 3.088 and 3.056 eV, on the basis of the excitation intensity dependence.
MOVPE, Cubic GaN, Photoluminescence, Excitonic transition, DA pair transition, Free to bound transition

Photoluminescence and photoluminescence-excitation spectroscopy of GaPAsN/GaP lattice-matched multiple quantum well structures
,Journal of Crystal Growth,195(1-4):574-578 1998
G. Biwa, H. Yaguchi, K. Onabe and Y. Shiraki
GaP1-x-yAsyNx/GaP (x=2.0%, y=12%) lattice-matched multiple quantum well (MQW) structures have been grown by metalorganic vapor-phase epitaxy (MOVPE). Low-temperature photoluminescence (PL) and photoluminescence excitation (PLE) measurements for the varied well widths (Lz=36, 24, and 16 AA) have revealed that the quantum confinement effect to the well manifests itself only in the narrow wells whose width is comparable with or shorter than the spatial extent of the localized excitons. Higher-temperature luminescence has been drastically enhanced, where the room temperature PL intensity is estimated 103-104 times larger than in the bulk. This is due to the efficient electron confinement to the well which is brought about by the large conduction band offset Delta Ec (~280 meV).
GaPAsN, Nitride alloy, Metalorganic vapor-phase epitaxy (MOVPE), Multiple quantum well (MQW), Photoluminescence (PL), Photoluminescence excitation spectroscopy (PLE)

Polarization Characteristics of Crescent-Shaped Tensile-Strained GaAsP/AlGaAs Quantum Wire-Like Lasers
,Japanese Journal of Applied Physics,37(3B):1556-1558 1998
M. Ishikawa, W. Pan, Y. Kaneko, H. Yaguchi, K. Onabe, R. Ito and Y. Shiraki
Crescent-shaped tensile-strained GaAsP/AlGaAs quantum wire-like lasers are fabricated on V-grooved GaAs(100) substrates by metalorganic vapor phase epitaxy. Light-output versus current characteristics, polarized lasing spectra and near-field patterns show lasing from the quantum wires in the TM mode. The threshold current density per wire is as low as 500 A/cm2 and the lasing wavelength is 780 nm.
tensile strain, quantum wire laser, TM polarization

Self-Assembled, Very Long II-VI Semiconductor Quantum Wires
,Materials Science & Engineering B,51(1-3):224-228 1998
B.P. Zhang, W.X. Wang, T. Yasuda, Y. Segawa, H. Yaguchi, K. Onabe, K. Edamatsu, T. Itoh
Self-organized ZnCdSe quantum wires (QWRs) are realized on cleavage-induced GaAs (110) surfaces based on simultaneous selective growth and composition modulation. Formed on step tops, the QWRs are parallel to the [110] direction and extend to millimeter order in length. Surface observations and optical studies demonstrate the formation of QWRs. A large piezo-electric field is observed in the QWRs, implying potential applications in nonlinear optoelectronic devices.
Quantum wires, Self-organized, Piezo-electric field

Sublattice Reversal in GaAs/Si/GaAs (100) Heterostructures by Molecular Beam Epitaxy
,Japanese Journal of Applied Physics,37(12B):L1493-1496 1998
S. Koh, T. Kondo, T. Ishiwada, C. Iwamoto, H. Ichinose, H. Yaguchi, T. Usami, Y. Shiraki and R. Ito
Sublattice reversal in III-V compound semiconductors grown on group-IV epitaxial layers on III-V substrates has been proposed for fabricating nonlinear optical devices with domain-inverted compound semiconductor structures. Sublattice reversal epitaxy is demonstrated in the GaAs/Si/GaAs(100) system and confirmed by reflection high energy electron diffraction, cross-sectional transmission electron microscopy, anisotropic etching, and optical second-harmonic generation measurements. The present sublattice reversal seems to be assisted by self annihilation of antiphase domains generated at GaAs/Si interfaces.
sublattice reversal, domain inversion, molecular beam epitaxy, antiphase domain, nonlinear optics, second-harmonic generation, quasi phase matching

Temperature dependence of photoluminescence of GaP1-xNx alloys
,Journal of Crystal Growth,189/190:496-499 1998
H. Yaguchi, G. Biwa, S. Miyoshi, D. Aoki, K. Arimoto, K. Onabe, R. Ito and Y. Shiraki
We report on the temperature dependence of photoluminescence (PL) in GaP1-xNx alloys. With increasing temperature the feature of the PL spectrum changes considerably and the luminescence with lower energies becomes predominant. This is explained by thermal activation processes from localized states to the state where excitons can move freely. By estimating the activation energies from the temperature dependence of the PL intensity, it is found that the state where excitons can move freely is formed below the band edge of GaP and shifts to lower energies with increasing nitrogen content. This state is considered to originate from the isoelectronic trap due to isolated nitrogens in GaP (A line) and correspond to the band edge of the GaP1-xNx alloy system.
GaPN, Band gap, Photoluminescence

Theoretical Study of Conduction Band Edge Formation in GaP1-xNx Alloys Using a Tight-Binding Approximation
,Journal of Crystal Growth,189/190:500-504 1998
H. Yaguchi
The conduction band edge formation in GaP1-xNx alloys is theoretically studied using a tight-binding method. The electronic structure of GaP1-xNx ordered alloys whose units-cell size is a*a*na (n=1-5) is calculated. The calculation confirmed that the conduction band edge formation in Ga1-xNx alloys originates from the formation of the A line. Localization at the N atoms is also discussed.
GaPN, Tight-binding method, Conduction band, Alloy, Localization

カソードルミネッセンスによる半導体低次元構造の評価
,電子顕微鏡,33:217-220 1998
矢口裕之,辻川智子,尾鍋研太郎
We have used cathodoluminescence to study various kinds of semiconductor low dimensional structures such as quantum wires and quantum dots. Several experimental results demonstrated that cathodoluminescence can reveal the spatial distribution of alloy composition or the origin of emissions and that it is a useful technique for the characterization of semiconductor low dimensional structures.

A highly luminescent crescent-shaped tensile-strained GaAsP/AlGaAs quantum wire laser structure
Elsevier,Journal of Crystal Growth,170(1-4):585-589 1997
W. Pan, H. Yaguchi, Y. Hanamaki, M. Ishikawa, Y. Kaneko, K. Onabe, R. Ito and Y. Shiraki
We report a highly luminescent crescent-shaped tensile-strained GaAsP/AlGaAs quantum wire (QWR) laser structure on 3 mu m periodic V-grooves grown by low-pressure (100 Torr) metalorganic vapor phase epitaxy (MOVPE). Photoluminescence studies show that carriers are efficiently captured from neighboring quantum well layers (QWLs) into QWRs, which give efficient luminescence. The QWR light emitting diode (LED) shows polarization insensitivity resulting from the tensile strain properties of the QWR structure.

Crystal Structure of GaN Grown on 3C-SiC Substrates by Metalorganic Vapor Phase Epitaxy
,Japanese Journal of Applied Physics,36(7A):4241-4245 1997
J. Wu, H. Yaguchi, H. Nagasawa, Y. Yamaguchi, K. Onabe, Y. Shiraki and R. Ito
GaN films were grown on 3C-SiC substrates by metalorganic vapor phase epitaxy (MOVPE) using 1,1-dimethylhydrazine (DMHy) as the N source. The crystal structure was strongly affected by both the growth temperature and the V/III ratio. At 600 degrees C, only hexagonal GaN films with their c-axis perpendicular to the substrate surface were grown. At 800 degrees C, relatively high V/III ratios resulted in the growth of hexagonal GaN with their c-axis oriented in the [111] direction while cubic GaN films were obtained at lower V/III ratios. The origin of [111]-oriented hexagonal GaN is also discussed.
MOVPE, GaN, cubic GaN, hexagonal GaN, 3C-SiC substrate 1,1-dimethylhydrazine (DMHy), X-ray diffraction

Electronic structure of (111)-GaAsP/AlGaAs strained-layer quantum wells
Elsevier,Surface Science,387(1-3):371-382 1997
X. Zhang, M. Ishikawa, H. Yaguchi and K. Onabe
The GaAs1-xPx/AlyGa1-yAs (x=0.07-0.14, y=0.3) strained-layer multiple quantum wells grown by metal-organic vapor phase epitaxy on GaAs-(111)B substrates have been characterized by X-ray diffraction and photoreflectance (PR) spectroscopy. By fitting the experimental results with the calculation which was based on the deformation potential theory modified by the strain-induced piezoelectric field, the energy band offset ratio for the conduction band at the heterointerface of GaAs1-xPx/AlyGa1-yAs was quantitatively determined to be Qc=0.61+or-0.03. This value was found to be nearly independent of the phosphorous composition x in the whole region that has been investigated in this study. Moreover, several anomalous phenomena observed with the PR measurement as well as the possible physical origins have also been discussed.

Growth Mechanism in the Metalorganic Vapor Phase Epitaxy of Metastable GaP1-xNx Alloys: A Growth Interruption Study
,Japanese Journal of Applied Physics,36(12A):7110-7118 1997
S. Miyoshi, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito
The metalorganic vapor phase epitaxy (MOVPE) of metastable GaP1-xNx alloys applying a growth interruption technique is performed. In the growth procedure, different from conventional MOVPE, a cycle of 1 ML growth and growth interruption (Ga precursor supply is turned off) is repeated. The nitrogen content (x) decreases with the increasing growth interruption time due to the desorption of nitrogen during the interruption. This means that the solid composition of the alloy is determined by the competition between the supply and the desorption of nitrogen at the film surface. The nitrogen adsorption/desorption model is presented. The time constant of the nitrogen desorption is obtained to be 0.47s at 670 degrees C. It is clarified that in the conventional (without growth interruption) MOVPE of the alloys, low growth temperature and high growth rate decrease the nitrogen desorption from the film surface and thus result in a large nitrogen content. We succeeded in growing the alloys with x as large as 6.3% by using a low growth temperature (650 degrees C) and a high growth rate (5 MLs/s).
MOVPE, GaP1-xNx, growth interruption, growth mechanism, nitrogen adsorption and desorption

In-plane polarization properties of GaAsP/AlAs strained quantum wells on GaAs(113)A and (114)A substrates
,Institute of Physics Conference Series,155:771-774 1997
N. Hiroyasu, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito
We have investigated the in-plane polarization properties of luminescence from GaAsP/AlAs tensile-strained quantum well structures grown on GaAs (113)A and (114)A substrates. With varying phosphorus composition or well width, the in-plane polarization changes significantly and reaches ~0.4 and ~0.3 for (113)A and (114)A substrates, respectively. It is found from the theoretical calculation that the large optical anisotropy is mainly due to the mixing of hole states induced by the strain effect.

Metalorganic Vapor Phase Epitaxy Growth Features of AlGaAs in Tetrahedral-Shaped Recesses on GaAs(111)B Substrates
,Japanese Journal of Applied Physics,36(6B):4102-4106 1997
T. Tsujikawa, W. Pan, K. Momma, M. Kudo, K. Tanaka, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito
We have investigated the compositional modulation of AlGaAs layers grown in tetrahedral-shaped recesses (TSRs) on n-type GaAs (111)B substrates using scanning electron microscopy, photoluminescence and cathodoluminescence. Growth hardly occurred between the TSRs, and complicated facets were seen in the TSR. Gallium-rich regions were formed around the edges between sidewalls rather than at the center of sidewalls and at the bottom region rather than the top region. To observe the facetting process during growth, GaAs/AlGaAs multi-layers were also grown in TSRs. Aluminum compositional modulation is dependent not only on the difference in migration distances of Ga and Al atoms but also on the differences in the incorporating process among different facets.
tetrahedral-shaped recess, Al composition, cathodoluminescence, migration distance, incorporation, facets

Naturally formed ZnCdSe quantum dots on ZnSe (110) surfaces
,Applied Physics Letters,70(18):2413-2415 1997
B. P. Zhang, T. Yasuda, Y. Segawa, H. Yaguchi, K. Onabe, E. Edamatsu and T. Itoh
We successfully realized ZnCdSe quantum dots on a cleavage-induced ZnSe (110) surface by depositing a ZnSe/ZnCdSe/ZnSe heterostructure under growth conditions that cannot lead to layer-by-layer growth of ZnSe. This growth mode introduces surface roughness to the newly deposited ZnSe layer, and ZnCdSe quantum dots are then formed. Cathodoluminescence and microphotoluminescence measurements demonstrate the formation of quantum dots.

Nitrogen concentration dependence of photoluminescence decay time in GaP1-xNx alloys
,Solid State Electronics,41(2):231-233 1997
H. Yaguchi, S. Miyoshi, H. Arimoto, S. Saito, H. Akiyama, K. Onabe, Y. Shiraki and R. Ito
We report on the nitrogen concentration dependence of photoluminescence (PL) properties in GaP1-xNx alloys. Time-resolved PL measurements reveal that the radiative transition and relaxation processes in GaP1-xNx alloys with high nitrogen concentrations are significantly different from those with low concentrations where NNi lines are clearly observed. The PL decay profile shows two distinct exponential processes with fast and slow decay times for high concentrations. With increasing N concentration, the fast decay component becomes dominant and the slow decay time becomes longer. The fast decay is attributed to the relaxation to nonradiative recombination centers. The slow decay indicates the long radiative lifetime due to the weak localization of excitons and the slow relaxation due to the scattered spatial distribution of the states. This is consistent with the fact that the PL occurs at the tails of the density of states.

Photoluminescence excitation spectroscopy of GaP1-xNx alloys: conduction-band-edge formation by nitrogen incorporation
,Journal of Crystal Growth,170(1-4):353-356 1997
H. Yaguchi, S. Miyoshi, G. Biwa, M. Kibune, K. Onabe, Y. Shiraki and R. Ito
We have investigated the conduction-band-edge formation in GaP1-xNx alloys by nitrogen incorporation into GaP using photoluminescence excitation (PLE) spectroscopy. The PLE spectra of GaP1-xNx alloys with various nitrogen concentrations show that the absorption edge shifts to lower energies with increasing nitrogen concentration. From the nitrogen concentration dependence of the absorption edge energy we found that the conduction-band-edge formation in GaP1-xNx alloys originates from the formation of the A line.

Photoluminescence properties of cubic GaN grown on GaAs(100) substrates by metalorganic vapor phase epitaxy
,Applied Physics Letters,71(15):2067-2069 1997
J. Wu, H. Yaguchi, K. Onabe, R. Ito and Y. Shiraki
Photoluminescence (PL) measurements were performed on cubic GaN films grown on GaAs(100) substrates by metalorganic vapor phase epitaxy. The cubic GaN films show a high optical quality that enables us to study the PL spectra in detail. From temperature and excitation intensity dependence, the emission lines at 3.274 and at 3.178 eV were assigned to the excitonic transition and the donor-acceptor pair transition, respectively. We also observed two additional emission lines at 3.088 and 3.056 eV. An excitonic emission at 3.216 eV with full width half maximum value as small as 73 meV was observed at 300 K.

Self Formation and Optical Properties of II-VI Semiconductor Wire Structures
,Japanese Journal of Applied Physics,36(11B):L1490-L1493 1997
B. Zhang, W. Wang, T. Yasuda, Y. Li, Y. Segawa, H. Yaguchi, K. Onabe, K. Edamatsu and T. Itoh
Based on simultaneous selective growth and composition modulation, Zn1-xCdxSe wire structures are spontaneously formed on cleavage-induced GaAs (110) surfaces by deposition of a Zn1-yCdySe (x>y) alloy layer. The wire structures are formed on the top edge of the steps introduced by cleavage. These wires show a strongly polarized emission and a large piezoelectric effect, implying a potential for applications in nonlinear optoelectronic devices. This paper discusses a novel approach to semiconductor nanostructures.
II–VI compound, MBE, selective growth, composition modulation, quantum wire

Self Formation and Photoluminescence of II-VI Quantum Wires on GaAs(110) Surfaces
,Nonlinear Optics,18(2-4):133-136 1997
B. P. Zhang, W. X. Wang, G. Isoya, T. Yasuda, Y. Segawa, H. Yaguchi, K. Onabe, K. Edamatsu and T. Itoh
Extremely long ZnCdSe quantum wires (QWR's) are naturally formed on cleavage-induced GaAs (110) surfaces by depositing simply one ZnCdSe alloy layer. The wires are parallel to the [-110] direction and extend to milimeter order in length. Surface observations and optical studies demonstrate the formation of QWR's. Large piezo-electric field is observed in the QWR's. This work provides a novel approach to self organized QWR's.

The Gammac-Gammav Transition Energies of AlxIn1-xP Alloys
,Japanese Journal of Applied Physics,36(11):6607-6613 1997
Y. Ishitani, H. Hamada, S. Minagawa, H. Yaguchi and Y. Shiraki
The transition energies at 20 K for the Gamma6c- Gamma7v (electron-heavy hole) (Eshh(x)) and for the Gamma6c- Gamma6v(1) (electron-light hole) (Es1h(x)) of strained and disordered AlxIn1-xP (0.43<or=x<or=0.62) on GaAs substrates were measured using a photoreflectance method. They are expressed as Eshh(x)=1.488(+or-0.020)+2.30(+or-0.04).x, and Es1h(x)=1.738(+or-0.030)+1.81(+or-0.06).x(eV). The Gamma6c- Gamma8v transition energies for unstrained layers (Eu(x)) were also measured at 20 K as Eu (x)=1.418(+or-0.007)+2.42(+or-0.01).x(eV). The unstrained samples were InP, Al0.53In0.47P on a GaAs substrate and Al0.73In0.27P on a GaAs0.61P0.39 substrate. The shift of the transition energies due to stress was obtained from these transition energies. The hydrostatic and shear deformation potentials for AlxIn1-xP alloys were calculated to be -5.23(+or-0.60) eV and -1.67(+or-0.26) eV by comparing the experimental results and the theoretical formulae.
AlxIn1-xP, electron-heavy hole transition energy, electron-light hole transition energy, strained alloy, unstrained alloy, disordered alloy, 20 K, hydrostatic and shear deformation potentials, photoreflectance, X-ray diffraction

Anomalous optical absorption in ZnCdSe/ZnSe single quantum wells
,Solid State Communications,99(12):897-900 1996
B. Zhang, T. Yasui, T. Yasuda, Y. Segawa, H. Yaguchi and Y. Shiraki
The optical absorption in ZnCdSe/ZnSe single quantum wells was studied by analyzing their reflectance spectra measured by a Fourier transform spectrometer. At lower temperatures, we observed a decrease in the excitonic absorption. This is qualitatively explained using a polariton model with the absorption dominated by phonon scattering. We present a comparison with III-V materials. The result confirms the polariton model of light propagation in quantum wells.

Characterization of Modulation-Doped n-AlxGa1-xAs/GaAs Heterostructure Using Spectroscopic Ellipsometry and Photoreflectance
SPIE,SPIE,2873:226-229 1996
C. C. Wong, M. Mochizuki, H. Yaguchi, T. Saitoh and Y.-M. Xiong
In this research the structural and electronic properties of a modulation-doped n-AlxGa1-xAs/GaAs heterostructure was nondestructively studied using spectroscopic ellipsometry (SE) and photoreflectance (PR). SE was used to characterize the thickness and Al composition x of the AlxGa1-xAs layer for the given sample. On the other hand, PR was used to determine the surface built-in electric field strength and the bandgap energy of the AlxGa1-xAs layer. The results of our analysis show that SE and PR, being complementary to each other, are useful methods in characterizing the given sample.

Characterization of Si delta-doped GaAs using photoellipsometry and photoreflectance
SPIE,SPIE,2873:270-273 1996
M. Mochizuki, K. Kobayashi, H. Yaguchi, T. Saitoh and Y.-M. Xiong
Photoellipsometry (PE), a contactless optical method, combines the features of both spectroscopic ellipsometry and photoreflectance (PR) and offers more complete information about the sample from a single experiment. PR, on the other hand, has been widely used for characterizing semiconductor microstructures. The nondestructive nature and the relatively sharper features produced in the measured spectra make this method very attractive. It was based on these advantages that we applied PE and PR to Si delta -doped GaAs. Two Si delta-doped GaAs samples were investigated in this study, each having an undoped GaAs cap layer of thickness L (L=100 and 200 nm, respectively). Our main objective was to determine built-in electric field strength in the cap layer of each sample. In the analysis of the measured PE spectra, the Franz-Keldysh (FK) theory was used, taking into account the broadening and the photovoltage effects, whereas the measured PR spectra were analyzed using the asymptotic form of an Airy function for the FK oscillations. The results of our analysis show that, for each sample studied, the field strength obtained from PE spectra is in good agreement with that determined from PR spectrum, and that the field strength decreases with the increase of the cap layer thickness.

Growth temperature dependence of AlGaAs spontaneous vertical quantum wells on V-grooved substrates by low-pressure metalorganic vapor phase epitaxy
Elsevier,Journal of Crystal Growth,158(3):205-209 1996
W. Pan, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito
We have studied the growth of AlGaAs on V-grooved GaAs substrates by low-pressure (100 Torr) metalorganic vapor phase epitaxy (MOVPE) in the temperature range of 600 to 700 degrees C. The growth temperature dependence of facet formation, the facet dependence of AlGaAs composition on the V-grooves, and the growth temperature dependence of spontaneous vertical quantum well (SVQW) widths have been investigated by low temperature photoluminescence (PL), transmission electron micrograph (TEM) and spectrally and spatially resolved low temperature cathodoluminescence (CL). The width of the SVQW varies from 140 to 250 AA with increasing the growth temperature from 600 to 700 degrees C.

Polarization properties of GaAsP/AlGaAs tensilely strained quantum wire structures grown on V-grooved GaAs substrates
Institute of Physics,Institute of Physics Conference Series,145:925-930 1996
W. Pan, H. Yaguchi, K. Onabe, R. Ito, N. Usami and Y. Shiraki
Crescent-shaped tensilely strained GaAs1-xPx/AlyGa1-yAs quantum wires (x=0.11, y=0.33) have been grown on 3-micro m-period V-grooved GaAs substrates by low-pressure metalorganic vapor phase epitaxy and characterized by cross-sectional transmission electron microscope observation, low temperature cross-sectional photoluminescence and cathodoluminescence. A drastic polarization transition from TM to TE with decreasing quantum wire size has been found in cross-sectional polarized photoluminescence.

Rectangular AlGaAs/AlAs Quantum Wires Using Spontaneous Vertical Quantum Wells
,Japanese Journal of Applied Physics,35(2B):1214-1216 1996
W. Pan, H. Yaguchi, K. Onabe, R. Ito, N. Usami, Y. Shiraki
We propose a lateral confinement enhanced rectangular AlGaAs/AlAs quantum wire (QWR) structure grown in situ, which utilizes the Ga-rich AlGaAs spontaneous vertical quantum wells formed during the growth of the AlGaAs epilayer in the V-grooves. AlGaAs/AlAs QWR structures have been grown on v-grooved substrates by low-pressure metalorganic vapor phase epitaxy (MOVPE), and been investigated by transmission electron microscopy, photoluminescence and cathodoluminescence measurements.
MOVPE, AlGaAs, quantum wire, spontaneous vertical quantum well, photoluminescence, cathodoluminescence

Strain effect on direct- and indirect-gap band lineups of GaAs1-xPx/GaP quantum wells
Institute of Physics,Institute of Physics Conference Series,145:403-408 1996
A. Shima, H. Yaguchi, S. Miyoshi, K. Onabe, Y. Shiraki and R. Ito
Strain effect on direct- and indirect-gap band lineups of strained GaAs1-xPx/GaP quantum wells with a wide range of x is studied using photoluminescence (PL) and photoreflectance (PR) spectroscopy. By comparing the transition energies obtained by PL and PR measurements with the calculation based on the effective mass approximation, it is found that the band lineups of strained GaAs1-xPx/GaP QWs on GaP substrates at any x are of type I at the X and Gamma point and that the valence band offset of heavy hole is 506(1-x) meV. As a result, it is deduced that biaxial compressive strain makes the energy gap of GaAS1-xPx alloys grown on GaP substrates indirect at any x.

The optical processes in AlInP/GaInP/AlInP quantum wells
American Institute of Physics,Journal of Applied Physics,80(8):4592-4598 1996
Y. Ishitani, S. Minagawa, T. Kita, T. Nishino, H. Yaguchi and Y. Shiraki
The optical processes in AlInP/GaInP/AlInP quantum wells free from long-range ordering are examined by photoluminescence (PL), photoluminescence excitation (PLE), and photoreflectance (PR) measurements. The PL method observes lower transition energy than the PLE and the PR methods which observe the space-averaged transition energy. This is because PL originates from localized lower-energy states to which an exciton state relaxes. By analyzing these measurements carried on 20- and 60-A-wide wells, the reason for this deviation is ascribed to the fluctuation of the transition energy due to the local variation of the well width by one molecular layer. The plausible share of the band offset for the conduction band against the energy gap difference at the Gamma point is obtained by comparing the experimentally obtained relative position of the energy levels in AlInP barriers and the 20 A GaInP well with the calculated ones. This is found to be 0.75 (+or-0.06).

Time-resolved photoluminescence study of radiative transition processes in GaP1-xNx alloys
Institute of Physics,Institute of Physics Conference Series,145:307-312 1996
H. Yaguchi, S. Miyoshi, H, Arimoto, S, Saito, H, Akiyama, K. Onabe, Y. Shiraki and R. Ito
Time-resolved photoluminescence (PL) measurements reveal that the radiative transition and carrier relaxation processes in GaP1-xNx alloys with high H concentrations are significantly different from those with low concentrations where NNi lines are clearly observed. The PL decay curve shows two distinct exponential processes for high concentrations while it is represented by a single exponential for low concentrations. The slow decay in GaP1-xNx alloys with high N concentrations indicates both the long radiative lifetime caused by the weak localization of excitons and the slow relaxation due to the scattered distribution of the states, This is consistent with the fact that the PL occurs at the tails of density of states, which is found from the comparison between absorption and PL spectra.

Time-resolved photoluminescence study on AlxGa1-xAs spontaneous vertical quantum well structures
American Institute of Physics,Applied Physics Letters,68(23):3221-3223 1996
N. Usami, W. Pan, H. Yaguchi, R. Ito, K. Onabe, H. Akiyama and Y. Shiraki
We report on time-resolved photoluminescence study of AlxGa1-xAs spontaneous vertical quantum well (SVQW) structures on GaAs V-grooved substrates. Four distinct photoluminescence peaks are observed originating from the spatial nonuniformity of the alloy compositions spontaneously formed during metalorganic vapor phase epitaxial growth. The decay time of the (111)A sidewall AlGaAs decreased with increasing temperature, while that of the SVQW increased. The rise time of the SVQW was found to be longer than the typical value of the exciton formation and increases with increasing temperature, indicating that the exciton formation is not limiting factor of the rise time. These results are explained in terms of the exciton diffusion toward the SVQW from the outer AlGaAs layers with less Ga compositions. In addition, two dimensionality of the SVQW was evidenced by temperature dependence of the radiative lifetime.

Composition profile of an AlGaAs epilayer on a V-grooved substrate grown by low-pressure metalorganic vapor phase epitaxy
American Institute of Physics,Applied Physics Letters,67(7):959-961 1995
W. Pan, H. Yaguchi, K. Onabe, R. Ito and Y. Shiraki
A composition distribution of an AlxGa1-xAs epilayer on a V-grooved substrate grown by low-pressure metalorganic vapor phase epitaxy is described. The aluminum (Al) content of an AlxGa1-xAs epilayer on a V-grooved substrate is found to be on the order of x(111)A>xtop(100)>xedge-facet>xbottom-intersection by using spectrally and spatially resolved low temperature cathodoluminescence (CL) measurements. The composition difference between (111)A surfaces and bottom intersections is as much as 30%. The resulting spontaneous vertical quantum wells and spontaneous waveguides in the bottom intersections are expected to be applicable in low-threshold current laser devices.

Growth parameters for metastable GaP1-xNx alloys in MOVPE
Institute of Physics,Institute of Physics Conference Series,141:97-100 1995
S. Miyoshi, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito
In order to clarify what determines the solid composition (x) in the metalorganic vapor phase epitaxy (MOVPE) of metastable GaP1-xNx alloys, we applied a growth interruption technique in this alloy growth. In our growth procedure, different from conventional MOVPE, the cycle of approximately 1 ML growth and growth interruption (only Ga precursor supply is turned off) is repeated. As increasing the growth interruption time, x decreases. This indicates that nitrogen atoms desorb from the film surface and that phosphorus atoms occupy the vacant sites during the growth interruption. The time constant of this substitution process is obtained to be 0.71, 0.47 and 0.39 sec at 655, 670 and 685 degrees C, respectively. This result can explain the growth temperature dependence and the growth rate dependence of x in the conventional MOVPE of this alloy system. It also gives a guide to growing the alloys with large x.

Optical property of GaAsP/AlGaAs strained-layer quantum well grown on GaAs-(111) B substrate
American Institute of Physics,Applied Physics Letters,66(2):186-188 1995
X. Zhang, K. Karaki, H. Yaguchi, K. Onabe, R. Ito and Y. Shiraki
GaAs1-xPx/AlyGa1-yAs (x=0.07-0.15, y=0.3) strained-layer quantum wells have been grown on GaAs-(111)B substrates by low-pressure metalorganic vapor phase epitaxy and characterized by photoluminescence (PL) spectroscopy. Evident energy blue shifts of the excitonic transition peaks (some of them as large as 33 meV) were achieved by increasing the excitation power during the PL measurement. The large optical nonlinearity mainly due to the strain-induced piezoelectric field screened by the photoexcited carriers, is comparable to, or larger than, the reported values for a self-electro-optical effect device or other (111)-oriented strained-layer quantum well structures which are composed of InGaAs/GaAs or GaAs/GaAsP. This fact indicates that our (111)-GaAsP/AlGaAs strained-layer quantum well is a good candidate for making optoelectronic devices like optical switches and modulators.

Reflectance spectroscopy of ZnCdSe/ZnSe single quantum wells
,RIKEN Review,11:23-24 1995
B. P. Zhang, T. Yasui, T. Yasuda, Y. Segawa, H. Yaguchi, Y. Shiraki
Exciton properties in ZnCdSe/ZnSe single quantum wells are studied by analyzing their reflectance spectra measured by a Fourier transform spectrometer. At lower temperatures, a decrease in the exciton absorption is observed. This is explained by a polariton model where the absorption is dominated by the phonon scattering. A comparison with III-V materials is presented. The result confirms the polariton model of light propagation in quantum wells.

Tensile-strained GaAsP/AlGaAs quantum wells grown by low-pressure metalorganic vapor phase epitaxy
American Institute of Physics,Journal of Applied Physics,78(5):3517-3519 1995
W. Pan, H. Yaguchi, K. Onabe, R. Ito and Y. Shiraki
Tensile-strained GaAs0.89Po0.11/Al0.33Ga0.67As quantum wells have been grown by low-pressure metalorganic vapor phase epitaxy. The grown samples have been studied by low-temperature (6 K) and 100 K in-plane photoluminescence as well as cross-sectional polarized photoluminescence measurements. The experimental results show the coincident or reversal point of the light- and heavy-hole related transitions at the well width of 60 AA, above which the low-temperature photoluminescence is given by the transition 1e-1lh. A theoretical calculation agrees well with the experimental results.

Characterization of Ge/SiGe Strained-Barrier Quantum Well Structures Using Photoreflectance Spectroscopy
American Physical Society,Physical Review B,49(11):7394-7399 1994
H. Yaguchi, K. Tai, K. Takemasa, K. Onabe, R. Ito and Y. Shiraki
We have investigated Ge/SiGe strained-barrier quantum-well structures using photoreflectance spectroscopy. On the basis of the Gamma -point transition energies associated with the Ge quantum well, the band offset at the heterojunction between Ge and SiGe has been found to vary linearly with the germanium composition in the SiGe barrier layer. The conduction-band-offset ratio Qc(= Delta Ec/( Delta Ec+ Delta Evh)) at the Gamma point is estimated to be 0.68+or-0.08. From the intrinsic linewidth of the quantum-well-related transitions, interface roughness has been characterized in this system and is estimated to be monolayer in our samples.

Determination of band offsets in GaAsP/GaP strained-layer quantum well structures using photoreflectance and photoluminescence spectroscopy
Institute of Physics,Institute of Physics Conference Series,136:361-366 1994
Y. Hara, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito
GaAs1-xPx (x=0.81,0.84,0.86)/GaP strained-layer quantum well (SLQW) structures have been studied using photoreflectance(PR) as well as photoluminescence(PL)) spectroscopy. The PR measurements have revealed the optical transitions between the quantized subbands in the higher-lying quantum well at the Gamma point. From the PR measurements, combined with a square-potential effective-mass calculation, the conduction band offset ratio has been determined to be 0.68+or-0.1 for x=0.84. This result leads to the type-I quantum well at the X-point conduction band minima. The low-temperature PL spectra are very consistent with the type-I band scheme.

Effect of growth interruption on the interface flatness in metalorganic vapor phase epitaxy-grown GaAs/GaAsP heterostructures
Elsevier,Journal of Crystal Growth,145(1-4):819-823 1994
K. Ota, H. Yaguchi, K. Onabe, R. Ito and Y. Shiraki
The interface flatness of metalorganic vapor phase epitaxy-grown GaAs/GaAsP strained barrier quantum wells has been studied with photoluminescence (PL). The PL peak clearly splits into two peaks when the growth rate is less than 1.7 AA/s or when the growth interruptions are introduced at the heterointerfaces. The energy separation between the two peaks corresponds to the well-width difference by a single monolayer. This indicates that the heterointerfaces are smoothed and that the islands of large lateral sizes are grown at the heterointerfaces. The growth interruption has been carried out either at the top (GaAsP on GaAs) or the bottom (GaAs on GaAsP) interface. It is found that the growth interruption is effective for smoothing both heterointerfaces. In addition, when the growth rate is 3.5 AA/s, the flatness of the growth front is retained during the growth of 90 AA layer.

Formation of Cubic GaN on (111)B GaAs by Metal-Organic Vapor-Phase Epitaxy with Dimethylhydrazine
,Japanese Journal of Applied Physics,33(6A):3415-3416 1994
N. Kuwano, K. Kobayashi, K. Oki, S. Miyoshi, H. Yaguchi, K. Onabe and Y. Shiraki
The microstructure of GaN grown on (111)B GaAs by a metal-organic vapor-phase epitaxy method has been examined by transmission electron microscopy. Trimethylgallium and dimethylhydrazine were used as the source materials. It was revealed that the GaN crystal has a zincblende structure and is formed heterogeneously penetrating into the GaAs substrate. In a GaN crystal, stacking faults propagate on (111) planes other than those normal to the growth direction.
cubic GaN, transmission electron microscopy, GaAs substrate, metal-organic vapor-phase epitaxy, dimethylhydrazine, deposit on (111)B, stacking fault, heterointerface

Intermediate range between N-doped GaP and GaP1-xNx alloys: difference in optical properties
Elsevier,Journal of Crystal Growth,145(1-4):87-92 1994
S. Miyoshi, H. Yaguchi, K. Onabe, R. Ito and Y. Shiraki
Metalorganic vapor phase epitaxy (MOVPE) grown GaP1-xNx metastable alloys with relatively dilute nitrogen concentrations (0.03%<x<1.4%, i.e.,  1*1019<[N]<3*1020 cm-3) have been studied with photoluninescence (PL). These nitrogen concentrations are especially interesting because they mdediate between the N-doped GaP([N]~1019 cm-3), where the PL should be associated with the band gap. The nitrogen concentration dependence of the PL spectra shows that the dominant emission changes from the shallow NNi centers (NN4, NN5) to the deepest one (NN1) with increasing x. The temperature dependence of the PL shows a similar systematic change in the spectrum. The integrated PL intensity versus x relationship indicates that at x>0.4% (approximately=1*1020 cm-3) nitrogen-doped GaP may be properly looked upon as a GaP1-xNx alloy.

Metalorganic vapor phase epitaxial growth and luminescence properties of GaAs/GaAsP quantum wires
Elsevier,Journal of Crystal Growth,145(1-4):702-706 1994
W. Pan, H. Yaguchi, K. Onabe, K. Wada, Y. Shiraki and R. Ito
Metalorganic vapor phase epitaxy (MOVPE) of GaAs/GaAsP quantum wires (QWRs) has been attempted on V-grooved GaAs (100) substrates. Intense photoluminescence (PL) from the wires as well as from the flat (100) quantum well layers (QWLs) has been obtained. The excitation-power dependence of the PL spectra confirms the efficient capture and confinement of free carriers in the wire regions. The top views of cathodoluminescence (CL) images show that the QWR structures have been successfully grown. The polarization of PL shows a strong optical anisotropy in QWRs due to two-dimensional quantum confinement. This is the first successful fabrication of GaAs/GaAsP QWR structures.

MOVPE growth of strained GaP1-xNx and GaP1-xNx/GaP quantum wells
Institute of Physics,Institute of Physics Conference Series,136:637-642 1994
S. Miyoshi, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito
We report the successful growth of GaP1-xNx (x<0.04) alloys on GaP by metalorganic vapor phase epitaxy (MOVPE). In spite of the large miscibility gap, which is calculated to extend from x=0.00001 to 0.99999 at 700 degrees C. GaP1-xNx alloys have been obtained at the growth temperature of 630 approximately 700 degrees C. The peak energy of low-temperature photoluminescence (PL) spectra shows a redshift with increasing x. We have made strained GaP1-xNx (well)/GaP (barrier) multiple quantum wells (MQWs) and observed strong PL emission from these MQWs.

Photoluminescence study of (111)-oriented GaAs/GaAsP strained-layer quantum well structure
American Institute of Physics,Applied Physics Letters,64(12):1555-1557 1994
X. Zhang, K. Karaki, H. Yaguchi, K. Onabe, R. Ito and Y. Shiraki
A GaAs/GaAs1-xPx (x=0.13) strained-layer quantum well structure has been grown on (111)B-oriented GaAs substrate by means of low-pressure (60 Torr) metalorganic vapor phase epitaxy and characterized by photoluminescence (PL) spectroscopy. Despite the partial relaxation of the tensile strain confined in the GaAsP barrier layers, our sample exhibits smooth surface morphology and intense optical emission. Moreover, an evident blue shift of the excitonic transition peak attributed to the screening of the strain-induced internal electric field by the photoexcited carriers, has been observed in the PL measurement.

Photoreflectance Study of Interface Roughness in Ge/SiGe Strained-Layer Heterostructures
,Japanese Journal of Applied Physics,33(4B):2353-2356 1994
H. Yaguchi, K. Tai, K. Takemasa, K. Onabe, Y. Shiraki and R. Ito
Ge/SiGe strained-layer heterostructures have been investigated using photoreflectance (PR) spectroscopy. On the basis of the comparison between the experimental and calculated quantum well-related transition energies formed at the Gamma point, band discontinuities at the Ge/SiGe heterojunction are determined and found to vary linearly with Ge content in the SiGe layer. Conduction band offset ratio Qc (= Delta Ec/( Delta Ec+ Delta EvHH)) at the Gamma point is evaluated to be 0.68+or-0.08. From the intrinsic linewidth of the quantum well-related transitions roughness at the Ge/SiGe heterointerface has been characterized for the first time and is estimated to be +or-1 monolayer (ML). In addition, the splittings in the PR spectra are observed in some samples at low temperatures. These splittings are due to the difference in the well width and correspond to the height (or depth) of about 10 ML.
Ge/SiGe heterointerface, photoreflectance, band offset, interface roughness, molecular beam epitaxy

Selective Growth of Cubic GaN in Small Areas on Patterned GaAs(100) Substrates by Metalorganic Vapor Phase Epitaxy
,Japanese Journal of Applied Physics,33(1B):694-697 1994
M. Nagahara, S. Miyoshi, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito
The metalorganic vapor phase epitaxy growth of cubic GaN in small areas on SiO2-patterned GaAs substrates has been performed. The authors have succeeded in selective growth without deposition on the SiO2 mask at temperatures between 620 and 675 degrees C. The crystal quality of cubic GaN has been improved through growth in small areas on patterned GaAs substrates. It is found that the grain size becomes larger and the full width at half maximum of the X-ray diffraction peak of cubic GaN becomes narrower on patterned substrates than on unpatterned ones.
cubic GaN, metalorganic vapor phase epitaxy, DMHy (dimethylhydrazine), patterned substrate, selective growth

Surface orientation dependence of growth rate of Cubic GaN
Elsevier,Journal of Crystal Growth,145(1-4):197-202 1994
M. Nagahara, S. Miyoshi, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito
The metalorganic vapor phase epitaxy (MOVPE) growth of cubic GaN has been performed on the patterned GaAs(100) substrates which have (111)A or (111)B facets. It is found that the growth features are strongly dependent on the configuration of the pattern. It is deduced that these features come from the surface-orientation-dependent growth rate, which is in the order (111)B>(100)>(111)A, combined with the diffusion of Ga adatoms on the surface. Taking advantage of the growth on the patterned substrates, the diffusion length of the Ga adatoms on the GaAs(100) surface is estimated to be several microns in the typical case.

Temperature dependence of photoluminescence linewidth in GaAs/GaAsP strained-layer quantum well structures
,Journal of Vacuum Science and Technology B,12(4):2293-2298 1994
X. Zhang, Y. Shiraki, H. Yaguchi, K. Onabe and R. Ito
The temperature dependence of photoluminescence (PL) spectra for the GaAs/GaAsP strained-layer single quantum well structures has been investigated in detail. For temperatures below 77 K, the PL linewidth was found to first decrease and then to increase slowly as the temperature was enhanced. This phenomenon was clearly seen for the GaAs/GaAsP strained-barrier quantum wells exhibiting higher dislocation densities than the GaAs/GaAsP strained-well quantum wells. This fact strongly suggests that beside the unintentionally introduced impurities, the misfit dislocations may also play an important role in determining the temperature-dependent PL linewidth.

Transmission Electron Microscope Observation of Cubic GaN Grown by Metalorganic Vapor Phase Epitaxy with Dimethylhydrazine on (001) GaAs
,Japanese Journal of Applied Physics,33(1A):18-22 1994
N. Kuwano, Y. Nagatomo, K. Kobayashi, K. Oki, S. Miyoshi, H. Yaguchi, K. Onabe and Y. Shiraki
Cross-sectional transmission electron microscope observation has been performed on the microstructure of GaN films grown on a (001) GaAs substrate by metalorganic vapor phase epitaxy (MOVPE) using 1,1-dimethylhydrazine (DMHy) and trimethylgallium (TMG) as the sources of nitrogen and gallium, respectively. Before the deposition, the surface of the substrate was nitrided with DMHy. High-resolution images and electron diffraction patterns confirmed that the GaN films have a zincblende structure ( beta -GaN) with the lattice constant of aGaN=0.454 nm, and contain bands of stacking faults parallel-to (111) planes. The interface between GaN and GaAs is made of (111) facets with no interlayer. Misfit dislocations are found to be inserted on the interface approximately every five atomic planes of GaAs. The nitridation treatment with only DMHy for 130 min is found to form a thick layer of beta -GaN on the (001) GaAs substrate. Nuclei of beta -GaN formed by the pretreatment of surface nitridation play an important role in growing GaN in a zincblende structure during the supply of DMHy and TMG. The formation of facets on the top surface of GaN and on the interface of GaN/GaAs is explained in terms of the diffusion of arsenic in beta -GaN. The characteristics of the structure of GaN films grown at 600 and 650 degrees C are also presented.
cubic GaN, metalorganic vapor phase epitaxy, transmission electron microscopy, stacking fault, high-resolution image, dimethylhydrazine, lattice parameter, facet of heterointerface, misfit dislocation, GaAs substrate

Valence-Subband Level Crossing in GaAs/GaAsP Strained-Barrier Quantum Well Structures Observed by Circularly Polarized Photoluminescence Excitation Spectroscopy
,Solid State Electronics,37(4-6):915-918 1994
H. Yaguchi, K. Ota, Y. Takahashi, K. Muraki, K. Onabe, Y. Shiraki and R. Ito
We have investigated the level configuration of the valence subbands in GaAs/GaAs1-xPx (x=0.23) strained-barrier quantum well structures as a function of the well width. Circularly polarized photoluminescence excitation (CPPLE) spectroscopy was used to identify the heavy- or light-hole character of the optical transitions. Distinct polarization properties were observed in the strain-split heavy-and light-hole hands in the GaAsP barriers; which indicates the photoexcited electrons in the barriers retain spin orientation well even after the capture into the well and the relaxation process. Utilizing this polarization tendency of the transitions in the barriers, we could distinguish unequivocally the heavy- and light-hole character of the quantum well-related transitions. By varying the well width systematically, we observed the level crossing between n=1 heavy- and light-hole transitions around the well width of 4 nm. This is in good agreement with the calculation based on the effective mass approximation.

GaAsP Layers Grown on (111)-Oriented GaAs Substrates by Metalorganic Vapor Phase Epitaxy
,Japanese Journal of Applied Physics,32(6A):L755-L757 1993
X. Zhang, K. Karaki, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito
High-quality GaAsP layers have been grown on (111)B GaAs substrates for the first time by means of low-pressure (60 Torr) metalorganic vapor phase epitaxy (MOVPE) and characterized by double-crystal X-ray diffraction and photoluminescence (PL) spectroscopy. Despite the large lattice mismatch between the GaAsP epitaxial layers and GaAs substrates, the GaAsP layers grown at higher temperature and higher V/III gas flow ratio as compared to the corresponding growth on a (100)-oriented GaAs substrate, exhibit smooth surface morphology, unambiguous X-ray diffraction peak, and intense optical emission.
MOVPE, GaAsP, X-ray diffraction, photoluminescence

Highly conductive p-type cubic GaN epitaxial films on GaAs
Institute of Physics,Institute of Physics Conference Series,129:79-84 1993
S. Miyoshi, N. Ohkouchi, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito
Electrical conduction in structure-transformed cubic undoped GaN films grown on (100) GaAs substrates grown by metalorganic vapor phase epitaxy has been investigated. P-type conduction in cubic films is presented for the first time. Film thickness dependence of Hall mobility and carrier concentration shows that film quality increases with increasing film thickness. Temperature dependence of these properties is measured. One explanation of p-type conduction is that carbon in the source materials (trimethylgallium and/or 1,1-dimethylhydrazine) has been incorporated into GaN films.

Intersubband absorption in n-type Si/Si1-xGex multiple quantum well structures formed by Sb segregant-assisted growth
Elsevier,Journal of Crystal Growth,127(1-4):416-420 1993
K. Fujita, S. Fukatsu, Y. Shiraki, H. Yaguchi and R. Ito
n-Si/Si1-xGex multiple quantum wells with 'abrupt' heterointerfaces have been created by segregant-assisted growth (SAG) using Sb. Distinct well-width dependence of intersubband absorption energy in thinner quantum wells (Lz=14-26 AA) has been successfully observed. The well-width dependence of the absorption peak energy was in good agreement with a calculation based on the Kronig-Penney model where interfacial transience was taken to be shorter than 0.4 nm. Present results show the potential power of SAG for creating 'abrupt' Si/Si1-xGex interfaces.

Is Low Temperature Growth the Solution to Abrupt S/Si1-xGex Interface Formation?
Elsevier,Journal of Crystal Growth,127(1-4):401-405 1993
S. Fukatsu, N. Usami, K. Fujita, H. Yaguchi, Y. Shiraki and R. Ito
Si/Si1-xGex interface transients were investigated with respect to the abruptness and smoothness by using sputter depth profiling (SIMS), X-ray photoemissions (XPS), photoluminescence and transmission electron microscopy. Ge segregation was confirmed by blue-shift of luminescence energy above what is expected in a square well potential, along with SIMS measurement. Ge segregation was found to persist even at 300 degrees C or lower. In contrast, Ge segregation was quenched by either segregant-assisted growth using Sb and Ga or solid-phase regrowth of Si cap layer; thereby a sharp Si/Si1-xGex interface was obtained. However, low-temperature-grown samples required an extensive anneal to restore band-edge luminescence, indicating a lack of quality of crystallinity.

Metal-Organic Vapor Phase Epitaxy Growth and Optical Study of GaAs/GaAs1-xPx Strained-Barrier Single Quantum Well Structures
Institute of Pure and Applied Physics,Japanese Journal of Applied Physics,32(3B):L375-L378 1993
X. Zhang, K. Onabe, H. Yaguchi, Y. Shiraki and R. Ito
GaAs/GaAs1-xPx (x=0.15, 0.20, 0.22) single quantum wells which involve tensile-strained GaAs1-xPx barrier layers have been grown on GaAs substrates by metal-organic vapor phase epitaxy (MOVPE) and characterized by double-crystal X-ray diffraction, photoluminescence (PL), and Fourier-transform reflectance spectroscopy (FT-RS). Despite the relatively large relaxation ratio of the strain (sometimes as high as 7.5%), these structures exhibit smooth surface morphology as well as intense and narrow excitonic emissions. The composition-dependent energy band offset ratios for the GaAs/GaAs1-xPx strained-barrier single quantum well structures have also been determined.

Metalorganic vapor phase epitaxy of GaP1-xNx alloys on GaP
American Institute of Physics,Applied Physics Letters,63(25):3506-3508 1993
S. Miyoshi, H. Yaguchi, K. Onabe, R. Ito and Y. Shiraki
We demonstrate a successful growth of GaP1−xNx alloys on GaP by metalorganic vapor phase epitaxy (MOVPE). This alloy system is predicted to have an extremely large miscibility gap, ranging from x=0.0000003 to 0.9999997 at 700 °C. However, metastable alloys (x<=0.04) have been obtained at the growth temperature of 630–700 °C. We focused on the growth condition dependence of solid composition (x). The nitrogen incorporation increases with decreasing growth temperature. It also increases with increasing growth rate, possibly due to nonequilibrium circumstances in the MOVPE growth. Low-temperature photoluminescence (PL) measurements show that the band gap of GaP1−xNx shifts to lower energy with increasing x.

Observation of the valence-subband level crossing in GaAs/GaAsP strained-barrier quantum well structures using circularly polarized photoluminescence excitation spectroscopy
American Institute of Physics,Applied Physics Letters,63(7):946-948 1993
K. Ota, H. Yaguchi, K. Onabe, R. Ito, Y. Takahashi, K. Muraki and Y. Shiraki
The authors have investigated the valence-subband level configuration in GaAs/GaAsP strained-barrier quantum wells as a function of the well width. As they systematically varied the well width, they observed the crossover behavior between the n=1 heavy- and light-hole states around the well width of 4 nm. Circularly polarized photoluminescence excitation (CPPLE) spectroscopy was used to identify the heavy- or light-hole character of the observed transitions. Distinct polarization properties were observed in the strain-split heavy- and light-hole states in the GaAsP barriers, which indicated that the photoexcited electrons in the barriers retained spin memory well even after the capture into the well through the relaxation process of energy and momentum. Taking advantage of this method, they were able to identify unequivocally the heavy- and light-hole characters of the transitions in the quantum well. The well-width dependence of the intersubband transition energies obtained by the CPPLE measurement is in good agreement with the calculation based on the effective mass approximation.

Photoreflectance Study of GaAs/GaAsP Strained-Barrier Quantum Well Structures
Institute of Pure and Applied Physics,Japanese Journal of Applied Physics,32(1B):544-547 1993
H. Yaguchi, X. Zhang, K. Ota, M. Nagahara, K. Onabe, Y. Shiraki and R. Ito
GaAs/GaAs1-xPx strained-barrier quantum well structures grown by metalorganic vapor phase epitaxy (MOVPE) have been investigated using photoreflectance (PR) spectroscopy. On the basis of the square-potential model, we have determined the band offsets at the heterojunction and their dependence on the phosphorus composition. It was found that in the GaAs/GaAs1-xPx strained-barrier quantum well, the band offsets are almost linearly dependent on the phosphorus composition in the range of x<0.23. In addition, it was derived that the conduction band offset ratio Qc=0.57 + or - 0.05. This result is consistent with our previous study concerning GaAs/GaAsP "strained-well" quantum well structures.
photoreflectance, GaAs, GaAsP, strained layer, quantum well, band offset, MOVPE, X-ray diffraction

Self-modulating Sb incorporation in Si/SiGe superlattices during molecular beam epitaxial growth
Elsevier,Surface Science,295(3):335-339 1993
K. Fujita, S. Fukatsu, N. Usami, Y. Shiraki, H. Yaguchi, R. Ito and K. Nakagawa
Self-modulating incorporation of Sb atoms has been found in Si/SiGe superlattices grown by conventional solid source Si molecular beam epitaxy. The origin of this phenomenon has been attributed to the difference in the segregation length of Sb atoms in Si and SiGe layers. It has been found that the segregation length of Sb in Si1-xGex layers increases as the Ge composition, x, increases and that Sb atoms are incorporated mainly in Si layers when Si/SiGe superlattices are grown.

Atomistic picture of interfacial mixing in the Si/Ge heterostructures
Elsevier,Surface Science,267(1-3):79-82 1992
S. Fukatsu, K. Fujita, H. Yaguchi, Y. Shiraki and R. Ito
Atomistic description of the interfacial mixing in the Si/Ge heterostructures during molecular beam epitaxial growth is presented. It is shown that the surface segregation of Ge atoms at the Si/Ge heterointerface is self-limited, i.e. controlled by Ge themselves, when their concentration is higher than 0.01 monolayer, due to the geometrical constraint arising from the surface bonding. In consequence, the Ge segregation exhibits a nonlinear behavior, which produces a non-exponential segregation profile. The Ge segregation is found to undergo a transition from a kinetically limited to an equilibrium regime around 400 degrees C at a growth rate of 0.1 mn/s.

Initial oxidation of MBE-grown Si(100) surfaces
Elsevier,Surface Science,275(3):395-400 1992
H. Yaguchi, K. Fujita, S. Fukatsu, Y. Shiraki, R. Ito, T. Igarashi and T. Hattori
The authors have investigated the initial oxidation of MBE-grown Si(100) surfaces with atomic flatness using X-ray photoemission spectroscopy (XPS) and reflection high energy electron diffraction (RHEED). It was found that the MBE-grown surfaces are inert and hardly oxidized even after exposure to molecular oxygen up to 1500 L at room temperature and that the oxygen coverage is saturated at 0.4 ML. At elevated temperatures, however, the surface oxidation was substantially promoted on the atomically flat surface. On the other hand, the oxidation was found to proceed on a deliberately corrugated Si surface prepared by a low temperature MBE growth, even at room temperature.

Intersubband absorption in narrow Si/SiGe multiple quantum wells without interfacial smearing
American Institute of Physics,Applied Physics Letters,61(2):210-212 1992
K. Fujita, S. Fukatsu, Y. Shiraki, H. Yaguchi and R. Ito
Si/Si1-xGex multiple quantum wells with abrupt heterointerfaces have been formed by segregant-assisted growth (SAG) with Sb. Distinct well-width dependence of intersubband absorption in the narrow quantum wells has been observed. The well-width dependence of the absorption peak energy is in good agreement with a calculation based on the Kronig-Penney model where interfacial smearing is taken to be less than 0.4 nm, suggesting the integrity of Si/Si1-xGex interfaces grown by SAG.

MOVPE growth of cubic GaN on GaAs using dimethylhydrazine
Elsevier,Journal of Crystal Growth,124(1-4):439-442 1992
S. Miyoshi, K. Onabe, N. Ohkouchi, H. Yaguchi, R. Ito, S. Fukatsu and Y. Shiraki
High-quality cubic GaN epitaxial films have been successfully grown on (100) GaAs substrates by metalorganic vapor phase epitaxy (MOVPE) using 1,1-dimethylhydrazine (DMHy) as the nitrogen source material. The full width at half maximum (FWHM) of the X-ray diffraction profile of 0.65 degrees has been obtained, which is the narrowest reported to date. The grown films were found to be made up of ridges with (111)B facets, with increasing film thickness. Raman peak characteristic of cubic symmetry has been obtained for the first time, showing that GaN films were of excellent quality.

Initial oxidation of MBE-grown Si surfaces
Materilas Research Society,Silicon Molecular Beam Epitaxy Symposium,651:35-39 1991
T. Igarashi, H. Yaguchi, K. Fujita, S. Fukatsu, Y. Shiraki and R. Ito and T. Hattori
The authors investigated the initial oxidation of MBE-grown Si(100) surfaces with atomic flatness using X-ray photoemission spectroscopy (XPS) and reflection high energy electron diffraction (RHEED). It was found that the MBE-grown surfaces are inert and hardly oxidized even after exposure to molecular oxygen up to 1500 Langmuir (L) at room temperature. At elevated temperatures, the surface oxidation was substantially promoted. On the contrary, the surface oxidation was found to be substantiated on a deliberately corrugated Si surface prepared by low temperature MBE growth, even at room temperature.

Involvement of the topmost Ge layer in the Ge surface segregation during Si/Ge heterostructure formation
American Institute of Physics,Applied Physics Letters,59(18):2240-2241 1991
K. Fujita, S. Fukatsu, H. Yaguchi, Y. Shiraki and R. Ito
Surface segregation of Ge atoms during Si/Ge heterostructure formation by molecular beam epitaxy has been investigated by X-ray photoemission spectroscopy varying the Ge layer thickness. It has been found that only the Ge atoms of the topmost layer are involved in the surface segregation, leaving the rest of the Ge atoms intact. This result supports the basic idea of the two-state-exchange model.

Kinetics of Ge segregation in the presence of Sb during molecular beam epitaxy
Materilas Research Society,Silicon Molecular Beam Epitaxy Symposium,651:217-222 1991
S. Fukatsu, K. Fujita, H. Yaguchi, Y. Shiraki and R. Ito
Kinetics of Ge segregation during molecular beam epitaxial growth is described. It is shown that the Ge segregation is self-limited in Si epitaxial overlayers due to a high concentration effect when the Ge concentration exceeds 0.01 monolayer (ML). As a result, segregation profiles of Ge are found to decay nonexponentially in the growth direction. This unusual Ge segregation was found to be suppressed with an adlayer of strong segregant, Sb, during the kinetic MBE growth. The authors develop a novel scheme to realize sharp Si/Ge interfaces with strong segregants. The lower limit of the effective amount of Sb for this was found to be 0.75 ML.

Self-limitation in the surface segregation of Ge atoms during Si molecular beam epitaxial growth
American Institute of Physics,Applied Physics Letters,59(17):2103-2105 1991
S. Fukatsu, K. Fujita, H. Yaguchi, Y. Shiraki and R. Ito
Self-limitation in the surface segregation of Ge atoms in the Si epitaxial overlayers arising from the surface bond geometry on Si(100) during molecular beam epitaxy has been investigated theoretically. It was found that Ge surface segregation is strongly limiting when the Ge concentration exceeds 0.01 monolayer. As a result of this self-limitation, segregation profiles of Ge in Si overlayers are found to decay nonexponentially in the growth direction with a kink in the profile around 3*1020 cm-3, which is in close agreement with the experimental observation. The kinetic barrier of the Ge surface segregation is estimated to be 1.63+or-0.1 eV.

Strain Relaxation in MBE-Grown Si1-xGex/Si(100) Heterostructures by Annealing
Institute of Pure and Applied Physics,Japanese Journal of Applied Physics,30(8B):L1450-L1453 1991
H. Yaguchi, K. Fujita, S. Fukatsu, Y. Shiraki and R. Ito
Strain relaxation in MBE-grown Si1-xGex/Si(100) strained-layer heterostructures by postgrowth annealing has been investigated using X-ray diffraction and Nomarski microscopy. The extent of the strain relaxation is found to be dependent on Ge composition and annealing temperatures. The strain relaxation model proposed by Dodson and Tsao is applied to our experimental data and good agreemnet is obtained.
strain relaxation, Si1-xGex/Si heterostructure, molecular beam epitaxy, misfit dislocation, X-ray diffraction, Nomarski microscopy

Suppression of interfacial mixing by Sb deposition in Si/Ge strained-layer superlattices
Materilas Research Society,Silicon Molecular Beam Epitaxy Symposium,651:193-197 1991
K. Fujita, S. Fukatsu, H. Yaguchi, T. Igarashi, Y. Shiraki and R. Ito
The authors have studied interfacial mixing of Si/Ge strained-layer superlattices during Si molecular beam epitaxy. The mixing has been shown to be primarily due to the surface segregation of Ge atoms during Si overlayer growth. It has been found that only the Ge atoms on the topmost Ge layer dominantly segregate to the growing surface. It has also been found that the surface segregation of Ge is effectively suppressed by depositing Sb atoms on the Ge layers. It has been demonstrated that Si/Ge superlattices with abrupt Si/Ge interfaces can be grown by depositing Sb. The two state exchange model is used to discuss the surface segregation of Ge and the suppression of the segregation by Sb deposition.

Realization of Abrupt Interfaces in Si/Ge Superlattices by Suppressing Ge Surface Segregation with Submonolayer of Sb
Institute of Pure and Applied Physics,Japanese Journal of Applied Physics,29(11):L1981-L1983 1990
K. Fujita, S. Fukatsu, H. Yaguchi, T. Igarashi, Y. Shiraki and R. Ito
Atomic mixing in Si/Ge strained-layer superlattices is investigated by means of SIMS and XPS. The interfacial mixing is attributed to the surface segregation of Ge atoms during MBE growth of Si overlayers. It is demonstrated that the surface segregation is remarkably suppressed by depositing submonolayer Sb atoms on Ge layers to Si overgrowth and that Ge layers are confined to within 0.8 nm.
Si/Ge strained-layer superlattice, surface segregation, molecular beam epitaxy, secondary ion mass spectrometry, X-ray photoemission spectroscopy

Pb/Si(111)表面超構造のRHEEDによる観察
日本表面科学会,表面科学,9(5):368-373 1988
H. Yaguchi, S. Baba and A. Kinbara
Pb/Si (111) surface superstructures have been studied using reflection high energy electron diffraction (RHEED) and molecular beam deposition techniques. The dependence of Pb/Si (111) surface structures on the Pb coverage and on the substrate temperature were elucidated on the basis of the RHEED observation in the coverage range from 0 ML to 2 ML and in the temperature range from 30 degree C to 500 degree C. In addition, we have measured changes in the RHEED intensities during Pb deposition. The results of the RHEED intensity measurements show that the saturation coverage for square root 3 times square root 3 (alpha) and square root 3 times square root 3 (beta) superstructures are 4/3 ML and 1/3 ML, respectively.

RHEED Study of Superstructures of Submonolayer Lead Films on Silicon(111) Surfaces
Elsevier,Applied Surface Science,33/34:75-80 1988
H. Yaguchi, S. Baba and A. Kinbara
Coverage and temperature dependences of Pb/Si(111) surface structure have been investigated using reflection high energy electron diffraction (RHEED) and molecular beam deposition techniques. With the deposition of Pb on a clean Si(111) surface in the temperature range between 30 and 500 degrees C, sequential changes in the RHEED pattern were observed in situ and thus a phase diagram of superstructures of submonolayer lead films on Si(111) surface could be established

RHEEDによるPb/Si(111)表面超構造の研究
日本真空協会,真空,31(5):399-401 1988
H. Yaguchi, S. Baba and A. Kinbara

学会発表
第一原理計算によるInAsN混晶のバンド構造に関する研究
第62回応用物理学会春季学術講演会 201503
宮崎貴史, 八木修平, 土方泰斗, 矢口裕之

GaAs:N δドープ超格子を有する太陽電池の二段階吸収
第62回応用物理学会春季学術講演会 201503
鈴木智也, 八木修平, 土方泰斗, 岡田至崇, 矢口裕之

4H-SiC(0001)微傾斜基板を用いたInNドット配列の自己形成
第62回応用物理学会春季学術講演会 201503
森誠也, 高宮健吾, 折原操, 八木修平, 土方泰斗, 矢口裕之

添加剤導入によるP3HT:PCBM混合膜の結晶成長過程のその場観察評価
第62回応用物理学会春季学術講演会 201503
新井康司, 柴田陽生, 伊藤英輔, 小金澤智之, 宮寺哲彦, 近松真之, 矢口裕之

Taming Spins in a Band-gap Engineered Germanium by Light Touch
2014 Workshop on Innovative Nanoscale Devices and Systems 201412
S. Hayashi, T. Tayagaki, Y. Okawa, Y. Yasutake, H. Yaguchi, Y. Kanemitsu, and S. Fukatsu

Control of Intermediate Band Configuration in GaAs:N δ-doped Superlattice
6th World Conference on Photovoltaic Energy Conversion 201411
K. Osada, T, Suzuki, S. Yagi, S. Naito, Y. Shoji, Y. Okada, Y. Hijikata, and H. Yaguchi

Molecular Beam Epitaxy Growth of Intermediate Band Materials Based on GaAs:N δ-Doped Superlattices
6th World Conference on Photovoltaic Energy Conversion 201411
T. Suzuki, K. Osada, S. Yagi, S. Naito, Y. Hijikata, Y. Okada, and H. Yaguchi

In -situ 分光エリプソメータによるSiC酸化過程の面方位依存性測定 (II)
先進パワー半導体分科会 第 1回講演会 201411
後藤大祐, 八木修平, 土方泰斗, 矢口裕之

フォトルミネッセンス法による4H -SiCエピ層中の酸化誘因欠陥観察
先進パワー半導体分科会 第 1回講演会 201411
宮野祐太郎, 八木修平, 土方泰斗, 矢口裕之

Photoluminescence Study of Oxidation-Induced Stacking Faults in 4H-SiC Epilayers
10th Europian Concerence on Silicon Carbide and Related Materilas 201409
Y. Miyano, S. Yagi, Y. Hijikata, H. Yaguchi

Surface orientation dependence of SiC oxidation process studied by in-situ spectroscopic ellipsometry
10th Europian Concerence on Silicon Carbide and Related Materilas 201409
D. Goto, S. Yagi, Y. Hijikata, H. Yaguchi

中間バンド型太陽電池に向けたGaAs:Nδドープ超格子のMBE成長
第75回応用物理学会秋季学術講演会 201409
鈴木智也, 長田一輝, 八木修平, 内藤俊弥, 土方泰斗, 岡田至崇, 矢口裕之

SiC酸化へのArアニール導入による酸化膜成長速度の変化
第75回応用物理学会秋季学術講演会 201409
今野良太郎, 八木修平, 土方泰斗, 矢口裕之

GaAs:N δドープ超格子による中間バンド構造のエネルギー制御
第75回応用物理学会秋季学術講演会 201409
長田一輝, 鈴木智也, 八木修平, 内藤駿弥, 庄司 靖, 岡田至崇, 土方泰斗, 矢口裕之

Geの磁場中時間分解円偏光フォトルミネッセンス
第75回応用物理学会秋季学術講演会 201409
安武裕輔, 矢口裕之, 深津 晋

Parallel-Antiparallel Spin Orientation Control In The Conduction Band Valleys Of Ge
Europian Materials Research Society 2014 Fall Meeting 201409
S. Hayashi, T. Tayagaki, Y. Okawa, Y. Yasutake, H. Yaguchi, Y. Kanemitsu, S. Fukatsu

二波長励起PLによるGaPN混晶の光学特性評価
平成26年度(第47回)照明学会全国大会 201409
末次 麻希子, A. Z. M. Touhidul Islam, 花岡 司, 福田 武司, 鎌田 憲彦, 八木 修平, 矢口 裕之

Luminescence and Quenching Properties in GaPN Revealed by Below-Gap Excitation
The 14th International Symposium on the Science and Technology of Lighting 201406
M. Suetsugu, A. Z. M. Touhidul Islam, T. Hanaoka, T. Fukuda, N. Kamata, S. Yagi, and H. Yaguchi

Resonant tunneling of electrons through cubic-InN quantum dots embedded in GaN
The 41st International Symposium on Compound Semiconductors 201405
S. Yagi, J. Suzuki, M. Orihara, Y. Hijikata, H. Yaguchi

Anomalous excitation power dependence of the luminescence from GaAsN/GaAs quantum well
The 41st International Symposium on Compound Semiconductors 201405
Y. Yamazaki, S. Yagi, Y. Hijikata, K. Onabe, H. Yaguchi

堆積と熱酸化による4H-SiC MOS構造の作製(II)
SiC及び関連半導体研究 第22回講演会 201312
大谷 篤志, 八木 修平, 土方 泰斗, 矢口 裕之

In-situ分光エリプソメーターによるSiC酸化過程の面方位依存性測定
SiC及び関連半導体研究 第22回講演会 201312
後藤大祐, 八木修平, 土方泰斗, 矢口裕之

薄膜作製展望:成膜過程における核生成過程の解明と制御の展開/総論
第42回薄膜・表面物理基礎講座 201311
矢口裕之

GaAs中窒素δドープ超格子の光学特性と中間バンド型太陽電池への応用
第9回量子ナノ材料セミナー 201311
八木修平, 矢口裕之

First-Principles Study of an Intermediate Band of GaPN Alloys
23rd International Photovoltaic Science and Engineering Conference 201311
M. Saito, K. Sakamoto, S. Yagi, H. Yaguchi

Fabrication and Characterization of Intermediate Band Solar Cells Using GaAs:N Delta-Doped Superlattice
23rd International Photovoltaic Science and Engineering Conference 201310
S. Yagi, S. Noguchi, Y. Hijikata, H. Yaguchi, S. Kuboya, K. Onabe, Y. Okada

Intermediate band solar cells based on GaAs:N δ-doped superlattices
4th International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures 201310
S. Yagi, S. Noguchi, Y. Hijikata, S. Kuboya, K. Onabe, Y. Okada, and H. Yaguchi

Excitation power dependence of the emission from various N-N pairs in N δ-doped GaAs
4th International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures 201310
K. Takamiya, S. Yagi, Y. Hijikata, T. Mochizuki, M. Yoshita, H. Akiyama, S. Kuboya, R. Katayama, K. Onabe, and H. Yaguchi

Si Emission into the Oxide Layer during Oxidation of Silicon Carbide
International Conference on Silicon Carbide and Related Materials 2013 201310
Y. Hijikata, Y. Akasaka, S. Yagi, and H. Yaguchi

第一原理計算によるGaAsN混晶の伝導帯の解析に関する研究
第74回応用物理学会秋季学術講演会 201309
坂本圭, 矢口裕之

窒素δドープGaAs中の単一等電子トラップによる励起子分子発光の時間分解フォトルミネッセンス測定
第74回応用物理学会秋季学術講演会 201309
高宮健吾, 八木修平, 土方泰斗, 望月敏光, 吉田正裕, 秋山英文, 窪谷茂幸, 片山竜二, 尾鍋研太郎, 矢口裕之

GaInNAs量子井戸の発光効率へのレーザー照射の影響
第74回応用物理学会秋季学術講演会 201309
岩崎卓也, 八木修平, 土方泰斗, 矢口裕之, 上田修

GaAsN/GaAs量子井戸構造からの発光の励起強度依存性
第74回応用物理学会秋季学術講演会 201309
山崎泰由, 八木修平, 土方泰斗, 尾鍋研太郎, 矢口裕之

六方晶SiC無極性面の酸化過程の実時間観察
第74回応用物理学会秋季学術講演会 201309
後藤大祐, 八木修平, 土方泰斗, 矢口裕之

GaAs:N δドープ超格子を用いた中間バンド型太陽電池の特性評価
第74回応用物理学会秋季学術講演会 201309
八木修平, 野口駿介, 土方泰斗, 窪谷茂幸, 尾鍋研太郎, 岡田至崇, 矢口裕之

InN/GaNドット多重積層構造に向けたGaNキャップ層成長条件の検討
第74回応用物理学会秋季学術講演会 201309
徳田英俊, 折原操, 八木修平, 土方泰斗, 矢口裕之

Ge/SiGe多重量子井戸への室温光スピン注入
第74回応用物理学会秋季学術講演会 201309
安武裕輔, 矢口裕之, 深津晋

Photoreflectance Study of the Temperature Dependence of Excitonic Transitions in Dilute GaAsN Alloys
10th International Conference on Nitride Semiconductors 2013 201308
W. Okubo, S. Yagi, Y. Hijikata, K. Onabe and H. Yaguchi

First Principles Study on the Conduction Band Electron States of GaAsN Alloys
10th International Conference on Nitride Semiconductors 2013 201308
K. Sakamoto and H. Yaguchi

Optical Absorption by E+ Miniband of GaAs:N Delta-Doped Superlattices
39th IEEE Photovoltaic Specialsits Conference 201306
S. Yagi, S. Noguchi, Y. Hijikata, S. Kuboya, K. Onabe, Y. Okada, H. Yaguchi

SiC酸化メカニズム解明への試み ~ Si酸化との共通点/異なる点 ~
電子情報通信学会シリコン材料・デバイス研究会 201306
土方泰斗, 八木修平, 矢口裕之

Stacked Structure of Self-Organized Cubic InN Nano-Scale Dots Grown by Molecular Beam Epitaxy
The 40th International Symposium on Compound Semiconductors 201305
S. Yagi, J. Suzuki, M. Orihara, Y. Hijikata, and H. Yaguchi

4H-SiCエピ膜中積層欠陥への熱酸化の影響について
第60回応用物理学関係連合講演会 201303
宮野祐太郎, 矢口裕之, 土方泰斗, 八木修平

第一原理計算によるGaPN混晶の電子構造解析
第60回応用物理学関係連合講演会 201303
齋藤誠, 坂本圭, 矢口裕之

中間バンド型太陽電池へ向けたGaAs中窒素δドープ超格子のE+バンド光吸収の観測
第60回応用物理学関係連合講演会 201303
野口駿介, 八木修平, 土方泰斗, 窪谷茂幸, 岡田至崇, 尾鍋研太郎, 矢口裕之

立方晶AlNおよび高Al濃度立方晶AlGaNのRF-MBE成長
第60回応用物理学関係連合講演会 201303
角田雅弘, 森川生, 窪谷茂幸, 片山竜二, 矢口裕之, 尾鍋研太郎

RF-MBE法による立方晶InNドット積層構造の作製
第60回応用物理学関係連合講演会 201303
鈴木潤一郎, 折原操, 八木修平, 土方泰斗, 矢口裕之

RF-MBE法によるGaAs(110)基板上へのGaNの成長
第61回応用物理学会春季学術講演会 201303
五十嵐健, 折原 操, 八木修平, 土方泰斗, 窪谷茂幸, 片山竜二, 矢口裕之

二波長PL測定によるGaPN混晶の中間バンドの観測
第61回応用物理学会春季学術講演会 201303
末次麻希子, トウヒドル イスラム, 村越尚輝, 花岡 司, 鎌田憲彦, 矢口裕之

堆積と熱酸化による4H-SiC MOS 構造の作製
第21回SiC及び関連ワイドギャップ半導体研究会 201211
大谷 篤志, 八木 修平, 土方 泰斗, 矢口 裕之

Enhancement of High Energy Band Optical Transition in GaAs:N Delta-Doped Superlattices for Intermediate Band Solar Cells
International Union of Materials Research Societies - International Conference on Electronic Materials 2012 201209
S. Yagi, S. Noguchi, Y. Hijikata, S. Kuboya, K. Onabe and H. Yaguchi

RF-MBE growth of cubic InN quantum dots on cubic GaN
17th International Conference on Molecular Beam Epitaxy 201209
J. Suzuki, M. Orihara, S. Yagi, Y. Hijikata and H. Yaguchi

Molecular beam epitaxy of ErGaAs alloys on GaAs (001) substrates
17th International Conference on Molecular Beam Epitaxy 201209
R. G. Jin, S. Yagi, Y. Hijikata, S. Kuboya, K. Onabe, R. Katayama and H. Yaguchi

RF-MBE 法によるTiO2(001)基板上への立方晶GaNの成長
第73回応用物理学会学術講演会 201209
折原 操, 八木修平, 土方泰斗, 矢口裕之

第一原理計算によるGaAsNの電子構造に対する原子配置の影響に関する研究
第73回応用物理学会学術講演会 201209
坂本 圭, 八木修平, 土方泰斗, 矢口裕之

RF-MBE法によるGaAs(110)基板上への半極性InN成長に対する窒化の影響
第73回応用物理学会学術講演会 201209
五十嵐健, 折原 操, 八木修平, 土方泰斗, 矢口裕之

InN成長におけるInN高温バッファ層の効果に関する検討
第73回応用物理学会学術講演会 201209
増田 篤, 折原 操, 八木修平, 土方泰斗, 矢口裕之

窒素δドープGaAs中の単一等電子トラップからの発光のフォトルミネッセ ンス励起分光測定
第73回応用物理学会学術講演会 201209
高宮健吾, 八木修平, 土方泰斗, 望月敏光, 吉田正裕, 秋山英文, 窪谷茂幸, 尾鍋研太郎, 片山竜二, 矢口裕之

MBE法によるGaAs(001)基板上へのErGaAs混晶の成長
第73回応用物理学会学術講演会 201209
金 日国, 八木修平, 土方泰斗, 窪谷茂幸, 尾鍋研太郎, 片山竜二, 矢口裕之

逆構造型有機薄膜太陽電池による高性能化への検討
第73回応用物理学会学術講演会 201209
小江宏幸, 河津浩典, 金子哲也, 松井卓矢, 増田 淳, 矢口裕之, 吉田郵司

スパッタ薄膜成長による4H-SiC 基板中の非発光再結合中心生成
第73回応用物理学会学術講演会 201209
加藤寿悠, 八木修平, 土方泰斗, 矢口裕之

堆積と熱酸化による4H-SiC MOS 構造の作製
第73回応用物理学会学術講演会 201209
大谷篤志, 八木修平, 土方泰斗, 矢口裕之

Model calculations of SiC oxide growth rates at sub-atmospheric pressures using the Si and C emission model
European Conference on Silicon Carbide and Related Materials 201209
Y. Hijikata, S. Yagi, H. Yaguchi, S. Yoshida

Investigation of organic-inorganic hybrid solar cell using inverted-type organic photovoltaics
KJF International Conference on Organic Materials for Electronics and Photonics 2012 201208
H. Ogo, H. Kawatsu, T. Kaneko, T. Matsui, A. Masuda, H. Yaguchi, and Y. Yoshida

Characterization of Structural Defects in InN Film on 4H-SiC (0001) Grown by RF-MBE
International Union of Materials Research Society - International Conference in Asia 2012 201208
P. Jantawongrit, S. Sanorpim, H. Yaguchi, M. Orihara, and P. Limsuwan

Biexciton Emission from Single Isoelectronic Traps Formed by Nitrogen-Nitrogen Pairs in GaAs
31st International Conference on the Physics of Semiconductors 201208
K. Takamiya, T. Fukushima, S. Yagi, Y. Hijikata, T. Mochizuki, M. Yoshita, H. Akiyama, S. Kuboya, K. Onabe, R. Katayama, and H. Yaguchi

First Principles Study on the Effect of the Position of Nitrogen Atoms on the Electronic Structure of GaAsN
31st International Conference on the Physics of Semiconductors 201207
K. Sakamoto and H. Yaguchi

Analysis of the Energy Structure of Nitrogen Delta-Doped GaAs Superlattices for High-Efficiency Intermediate-Band Solar Cells
38th IEEE Photovoltaic Specialists Conference 201206
S. Noguchi, S. Yagi, Y. Hijikata, S. Kuboya, K. Onabe, and H. Yaguchi

RF-MBE法によるInN量子ドットの結晶構造制御
第4回窒化物半導体結晶成長講演会 201204
徳田英俊, 鈴木潤一郎, 折原操, 八木修平, 土方泰斗, 矢口裕之

熱酸化が4H-SiCエピ膜中積層欠陥に及ぼす影響の顕微フォトルミネッセンスによる観察
第59回応用物理学関係連合講演会 201203
山形 光,八木修平,土方泰斗,矢口裕之

窒素δドープGaAs中の窒素原子対が形成する単一の等電子トラップからの発光に対する一軸応力の影響
第59回応用物理学関係連合講演会 201203
新井佑也,星野真也,高宮健吾,八木修平,土方泰斗,望月敏光,吉田正裕,秋山英文,窪谷茂幸,尾鍋研太郎,矢口裕之

GaAs中窒素δドープ超格子のエネルギー構造評価
第59回応用物理学関係連合講演会 201203
野口駿介,八木修平,土方泰斗,窪谷茂幸,尾鍋研太郎,矢口裕之

窒素δドープGaAsにおける単一等電子トラップからの励起子分子発光
第59回応用物理学関係連合講演会 201203
高宮健吾,福島俊之,星野真也,八木修平,土方泰斗,望月敏光,吉田正裕,秋山英文,窪谷茂幸,片山竜二,尾鍋研太郎,矢口裕之

分光エリプソメトリによる立方晶InNの光学的特性評価
第59回応用物理学関係連合講演会 201203
吉田倫大,折原 操,八木修平,土方泰斗,矢口裕之

SiC熱酸化機構の解明への取り組み
第20回SiC及び関連ワイドギャップ半導体研究会 201112
土方泰斗, 矢口裕之, 吉田貞史

MOS構造の電気的特性に対する4H-SiCエピ層中積層欠陥の影響
第20回SiC及び関連ワイドギャップ半導体研究会 201112
外谷彰悟, 土方泰斗, 矢口裕之

顕微フォトルミネッセンスを用いた4H-SiCエピ膜中積層欠陥に対する酸化の影響に関する研究
第20回SiC及び関連ワイドギャップ半導体研究会 201112
山形光, 土方泰斗, 矢口裕之

Effect of Thermal Current at Selective Contacts Using Resonant Tunneling Structures on Perfornance of Hot Carrier Solar Cells
21st International Photovoltaic Science and Engineering Conference 201111
S. Yagi, Y. Hijikata, Y. Okada, and H. Yaguchi

量子ドット太陽電池に向けた立方晶GaN上への立方晶InNドット配列成長
第3回薄膜太陽電池セミナー 201110
鈴木潤一郎,折原操,八木修平,土方泰斗,矢口裕之

Biexciton Emission from Single Isoelectronic Traps in Nitrogen Atomic-Layey-Doped GaAs
3rd International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures 201109
K. Takamiya, T. Fukushima, S. Yagi, Y. Hijikata, T. Mochizuki, M. Yoshita, H. Akiyama, S. Kuboya, K. Onabe, R. Katayama and H. Yaguchi

共鳴トンネル構造を用いたエネルギー選択層における熱励起電流のホットキャリア型太陽電池特性への影響
第72回応用物理学会学術講演会 201109
八木修平, 土方泰斗, 岡田至崇, 矢口裕之

SiCの2段階酸化における酸化膜成長速度の測定
第72回応用物理学会学術講演会 201108
篠田 龍, 土方泰斗, 矢口裕之, 八木修平, 吉田貞史

RF-MBE法による立方晶GaN上への立方晶InNドットの成長(II)
第72回応用物理学会学術講演会 201108
鈴木潤一郎, 折原 操, 八木修平, 土方泰斗, 矢口裕之

RF-MBE法によるInN(10-13)及びInGaN(10-13)のGaAs(110)基板上への成長
第72回応用物理学会学術講演会 201108
折原 操, 八木修平, 土方泰斗, 矢口裕之

窒素δドープGaAs(110)中の単一等電子トラップからの発光の偏光特性
第72回応用物理学会学術講演会 201108
高宮健吾, 福島俊之, 星野真也, 八木修平, 土方泰斗, 望月敏光, 吉田正裕, 秋山英文, 窪谷茂幸, 片山竜二, 尾鍋研太郎, 矢口裕之

Single Photon Generation from Nitrogen Atomic-Layer Doped Gallium Arsenide
7th International Conference on Processing & Manufacturing of Advanced Materials 201108
K. Takamiya, Y. Endo, T. Fukushima, S. Yagi, Y. Hijikata, T. Mochizuki, M. Yoshita, H. Akiyama, S. Kuboya, K. Onabe, R. Katayama, and H. Yaguchi

RF-MBE Growth of Semipolar InN(10-13) and InGaN(10-13) on GaAs(110)
9th International Conference on Nitride Semiconductors 201107
M. Orihara, S. Yagi, Y. Hijikata, H. Yaguchi

Quantum Well Double Barrier Resonant Tunneling Structures for Selective Contacts of Hot Carrier Solar Cells
37th IEEE Photovoltaic Specialists Conference 201106
S. Yagi, Y. Hijikata, Y. Okada, H. Yaguchi

TEM analysis of hexagonal-phase induction in MBE grown cubic InN layer on MgO (001) using a cubic GaN buffer layer
38th International Symposium on Compound Semiconductors 201105
Jamreonta Parinyataramas, Sakuntam Sanorpim, Visittapong Yordsri, Chanchana Thanachayanont, Hiroyuki Yaguchi, Misao Orihara

Characterization of substrate off-angle effects for high-quality InN films grown by RF-MBE on 4H-SiC (0001)
38th International Symposium on Compound Semiconductors 201105
Papaporn Jantawongrit, Sakuntam Sanorpim, Hiroyuki Yaguchi, Misao Orihara, Pichet Limsuwan

GaAs(110)基板上に作製した窒素δドープGaAsにおける等電子トラップからの発光特性評価
第58回応用物理学関係連合講演会,第58回応用物理学関係連合講演会 講演予稿集:25p-BQ-4 201103
高宮健吾,福島俊之,星野真也,八木修平,土方泰斗,望月敏光,吉田正裕,秋山英文,窪谷茂幸,片山竜二,尾鍋研太郎,矢口裕之

InN/p-4H-SiC構造の作製と電気・光学特性評価
第58回応用物理学関係連合講演会,第58回応用物理学関係連合講演会 講演予稿集:25a-BY-7 201103
矢野貴大,折原 操,八木修平,土方泰斗,矢口裕之

RF-MBE法による立方晶GaN上への立方晶InNドットの成長
第58回応用物理学関係連合講演会,第58回応用物理学関係連合講演会 講演予稿集:26p-BZ-2 201103
鈴木潤一郎,折原 操,八木修平,土方泰斗,矢口裕之

SiC熱酸化機構の解明への取り組み:特にSi酸化との類似点及び相違点について
第58回応用物理学関係連合講演会,第58回応用物理学関係連合講演会 講演予稿集:24p-BN-11 201103
土方泰斗,矢口裕之,吉田貞史

Single photon emission from nitrogen delta-doped semiconductors
SPIE Photonics West OPTO,SPIE Photonics West OPTO 201101
Hiroyuki Yaguchi

In-situ 分光エリプソメ−タによるSiC 酸化過程の酸素分圧依存性測定
SiC及び関連ワイドギャップ半導体研究会,SiC 及び関連ワイドギャップ半導体研究会第19回講演会 201010
甲田景子、土方泰斗、矢口裕之、吉田貞史

酸化中のSiC層へのSiおよびC原子放出についての理論的検討
第71回応用物理学会学術講演会,第71回応用物理学会学術講演会 講演予稿集:15a-ZS-10 201009
土方泰斗,八木修平,矢口裕之,吉田貞史

極低窒素濃度GaAsNにおける窒素ペアからの発光の窒素濃度依存性 (14p-ZV-3) (長崎) 2010. 9. 14
第71回応用物理学会学術講演会,第71回応用物理学会学術講演会 講演予稿集:14p-ZV-3 201009
石川 輝,八木修平,土方泰斗,吉田貞史,岡野真人,望月敏光,吉田正裕,秋山英文,窪谷茂幸,尾鍋研太郎,片山竜二,矢口裕之

極低窒素濃度GaAsNのフォトリフレクタンススペクトル
第71回応用物理学会学術講演会,第71回応用物理学会学術講演会 講演予稿集:14p-ZV-1 201009
大久保航,石川 輝,八木修平,土方泰斗,吉田貞史,片山竜二,尾鍋研太郎,矢口裕之

極低窒素濃度GaAsN中の等電子トラップからの発光に対する一軸応力の影響
第71回応用物理学会学術講演会,第71回応用物理学会学術講演会 講演予稿集:14p-ZV-2 201009
新井佑也,遠藤雄太,八木修平,土方泰斗,窪谷茂幸,尾鍋研太郎,片山竜二,矢口裕之

窒素δドープGaAs/AlGaAsヘテロ構造における等電子トラップからの発光特性評価
第71回応用物理学会学術講演会,第71回応用物理学会学術講演会 講演予稿集:14p-ZV-6 201009
高宮健吾,遠藤雄太,福島俊之,星野真也,八木修平,土方泰斗,望月敏光,吉田正裕,秋山英文,窪谷茂幸,尾鍋研太郎,片山竜二,サノーピン サクンタム,矢口裕之

窒素δドープGaAs中の等電子トラップを形成する窒素原子対配列に関する研究
第71回応用物理学会学術講演会,第71回応用物理学会学術講演会 講演予稿集:14p-ZV-5 201009
星野真也,遠藤雄太,福島俊之,高宮健吾,八木修平,土方泰斗,望月敏光,吉田正裕,秋山英文,窪谷茂幸,尾鍋研太郎,片山竜二,矢口裕之

Theoretical studies for Si and C emission into SiC layer during oxidation
8th European Conference on Silicon Carbide and Related Materials 201008
Y. Hijikata, H. Yaguchi, and S. Yoshida

High cubic-phase purity InN on MgO (001) using cubic-phase GaN as buffer layer
30th International Conference on the Physics of Semiconductors 201007
S. Sanorpim, S. Kuntharin, H. Yaguchi, Y. Iwahashi, M. Orihara, Y. Hijakata, S. Yoshida

様々な面方位基板上に作製した窒素δドープGaAs中の等電子トラップからの発光(III)
第56回応用物理学関係連合講演会 201003
福島俊之,高宮健吾,土方泰斗,矢口裕之,吉田貞史,岡野真人,吉田正裕,秋山英文,窪谷茂幸,尾鍋研太郎,片山竜二

4H-SiC/酸化膜界面の光学的および電気的評価
SiC及び関連ワイドギャップ半導体研究会,SiC及び関連ワイドギャップ半導体研究会第18回講演会:P-32 200912
若林敬浩, 土方泰斗, 矢口裕之, 吉田貞史
神戸 2009. 12. 17

In-situ分光エリプソメータによる低酸素分圧下におけるSiC酸化過程の観察
SiC及び関連ワイドギャップ半導体研究会,SiC及び関連ワイドギャップ半導体研究会第18回講演会:P-26 200912
甲田景子, 土方泰斗, 矢口裕之 吉田貞史

SiおよびC原子放出モデルに基づく様々な酸化温度におけるSiC 酸化速度のモデル計算
SiC及び関連ワイドギャップ半導体研究会,SiC及び関連ワイドギャップ半導体研究会第18回講演会:P-72 200912
土方泰斗、矢口裕之、吉田貞史
神戸 2009. 12. 17

RF-MBE Growth of InN on 4H-SiC(0001) with Off-angles
The 8th International Conference on Nitride Semiconductors,The 8th International Conference on Nitride Semiconductors Abstract Book,2:1112-1113 200910
M.Orihara, S.Takizawa, T.Sato, Y.Ishida, S.Yoshida, Y.Hijikata, H.Yaguchi

Model calculation of SiC oxide growth rate at various oxidation temperatures based on the silicon and carbon emission model
International Conference on Silicon Carbide and Related Materials 2009,International Conference on Silicon Carbide and Related Materials 2009:Th-3B-5 200910
Y.Hijikata, H.Yaguchi, S.Yoshida

In-situ Spectroscopic Ellipsometry Study of SiC Oxidation at Low Oxygen-Partial-Pressures
International Conference on Silicon Carbide and Related Materials 2009,International Conference on Silicon Carbide and Related Materials 2009:Tu-P-40 200910
K. Kouda, Y. Hijikata, H. Yaguchi, S. Yoshida

In-situ分光エリプソメ タによる低酸素分圧下におけるSiC酸化過程の観察
第70回応用物理学会学術講演会,第70回応用物理学会学術講演会,1:384 (10p-M-11) 200909
甲田景子、土方泰斗、矢口裕之、吉田貞史

RF-MBE法による4H-SiC(0001)オフ基板上へのInN直接成長
第70回応用物理学会学術講演会,第70回応用物理学会学術講演会,1:345 (10p-E-2) 200909
折原操、瀧澤伸、佐藤貴紀、石田夕起、吉田貞史、土方泰斗、矢口裕之

フォトリフレクタンスによるGaAsNの電子構造に関する研究
第70回応用物理学会学術講演会,第70回応用物理学会学術講演会,1:303 (9p-C-6) 200909
大久保航,土方泰斗,矢口裕之,吉田貞史,片山竜二,尾鍋研太郎

極低窒素濃度GaAsNのフォトルミネッセンス励起分光測定
第70回応用物理学会学術講演会,第70回応用物理学会学術講演会,1:305 (9p-C-11) 200909
石川 輝,土方泰斗,矢口裕之,吉田貞史,岡野真人,吉田正裕,秋山英文,窪谷茂幸,尾鍋研太郎,片山竜二

窒素δドープGaAs/AlGaAsヘテロ構造における等電子トラップからの発光
第70回応用物理学会学術講演会,第70回応用物理学会学術講演会,1:305 (9p-C-12) 200909
高宮健吾,遠藤雄太,福島俊之,土方泰斗,矢口裕之,吉田貞史,岡野真人,秋山英文,窪谷茂幸,尾鍋研太郎,片山竜二

Polarization properties of photoluminescence from individual isoelectronic traps in nitrogen delta-doped semiconductors: effect of host crystals
The Second International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor 200908
H.Yaguchi

GaAs(001)および(111)面基板上に作製した窒素δドープGaAs中の等電子トラップからの発光
第5回量子ナノ材料セミナー,第5回量子ナノ材料セミナー 200907
福島俊之, 矢口裕之

Photoluminescence from single isoelectronic traps in nitrogen delta-doped GaAs grown on GaAs(111)A
The 14th International Conference on Modulated Semiconductor Structures,The 14th International Conference on Modulated Semiconductor Structures:120 (Tu-mP5) 200907
T. Fukushima, M. Ito, Y. Hijikata, H. Yaguchi, S. Yoshida, M. Okano, M. Yoshita, H. Akiyama, S. Kuboya, R. Katayama, K. Onabe

InP(001)基板上へのInPN薄膜のMOVPE成長
応用物理学会,第56回応用物理学関係連合講演会 200903
関 裕紀,窪谷茂幸,クァントゥ ティユ,片山竜二,矢口裕之,尾鍋研太郎

窒素をδドープしたGaP中の等電子トラップからの発光(III)
応用物理学会,第56回応用物理学関係連合講演会 200903
伊藤正俊,福島俊之,土方泰斗,矢口裕之,吉田貞史,岡野真人,吉田正裕,秋山英文,窪谷茂幸,片山竜二,尾鍋研太郎

様々な面方位基板上に作製した窒素δドープGaAs中の等電子トラップからの発光(II)
応用物理学会,第56回応用物理学関係連合講演会 200903
福島俊之,伊藤正俊,土方泰斗,矢口裕之,吉田貞史,岡野真人,吉田正裕,秋山英文,窪谷茂幸,片山竜二,尾鍋研太郎

In-situ 分光エリプソメ-タによるSiC 酸化速度の酸素分圧依存性測定(II)
第56回応用物理学関係連合講演会,第56回応用物理学関係連合講演会講演予稿集 200903
甲田景子,高久英之,土方泰斗,矢口裕之,吉田貞史

界面Si及びC原子放出現象に基づくSiC酸化モデル
第56回応用物理学関係連合講演会,第56回応用物理学関係連合講演会講演予稿集 200903
土方泰斗,矢口裕之,吉田貞史

厚い酸化膜領域におけるSiCの酸化速度の測定
第56回応用物理学関係連合講演会,第56回応用物理学関係連合講演会講演予稿集 200903
若林敬浩,柴崎俊哉,土方泰斗,矢口裕之,吉田貞史

Characterization of 4H-SiC/SiO2 interfaces using a deep ultraviolet spectroscopic ellipsometer
,The 1st International Forum on Frontier Photonics:P-14 200903
T. Wakabayashi, H. Seki, Y. Hijikata, H. Yaguchi and S. Yoshida

Photoluminescence from isoelectronic traps in nitrogen delta-doped GaAs grown on variously oriented GaAs surfaces
,The 1st International Forum on Frontier Photonics:P-15 200903
T. Fukushima, M. Ito, Y. Hijikata, H. Yaguchi, S. Yoshida, M. Okano, M. Yoshita, H. Akiyama, S. Kuboya, R. Katayama and K. Onabe

Photoluminescence study of hexagonal InN/InGaN multiple quantum well structures grown on 3C-SiC (001) substrates by RF-MBE
,The 1st International Forum on Frontier Photonics:O-2 200903
H. Yaguchi, S. Hirano, M. Orihara, Y. Hijikata, and S. Yoshida

ラマン分光を用いたGaInAsN混晶の発光効率の変化に関する研究
応用物理学会,第55回応用物理学関係連合講演会:370 200803
谷岡健太郎,堀口歩,土方泰斗,矢口裕之,吉田貞史,片山竜二,尾鍋研太郎,吉田正裕,秋山英文

極低濃度窒素をドーピングしたGaAs中の等電子トラップからの発光
応用物理学会,第55回応用物理学関係連合講演会:368 200803
福島俊之,遠藤雄太,伊藤正俊,土方泰斗,矢口裕之,吉田貞史,吉田正裕,秋山英文,窪谷茂幸,片山竜二,尾鍋研太郎

In-situ分光エリプソメータによるSiCの極薄領域における酸化過程の観察
応用物理学会,第55回応用物理学関係連合講演会:432 200803
高久英之,山本健史,土方泰斗,矢口裕之,吉田貞史

多入射角分光エリプソメトリによるSiC/酸化膜界面の光学的評価
応用物理学会,第55回応用物理学関係連合講演会:432 200803
若林敬浩,関秀康,土方泰斗,矢口裕之,吉田貞史

分光エリプソメータによるSiO2/SiC界面の光学的評価 -酸化膜厚依存性-
応用物理学会,第55回応用物理学関係連合講演会:433 200803
関秀康,若林敬浩,土方泰斗,矢口裕之,吉田貞史

RF-MBE法により成長させたA面InN膜のフォトルミネッセンス特性
応用物理学会,第55回応用物理学関係連合講演会:383 200803
四方剛,井上赳,佐藤貴紀,平山秀樹,折原操,土方泰斗,矢口裕之,吉田貞史

RF-MBE法により成長した立方晶InNのPL測定 (II)
応用物理学会,第55回応用物理学関係連合講演会:380 200803
井上赳,四方剛,塚越裕介,富田康浩,中島洋,折原操,土方泰斗,矢口裕之,吉田貞史

RF-MBE法を用いた3C-SiC基板上への立方晶InNの結晶成長およびその物性評価
応用物理学会,第55回応用物理学関係連合講演会:380 200803
富田康浩,井上赳,折原操,土方泰斗,矢口裕之,吉田貞史,平林康男

In-situ 分光エリプソメータによるSiC の極薄膜厚領域における酸化過程の観察
SiC及び関連ワイドギャップ半導体研究会 第16回講演会 200711
高久英之、土方泰斗、矢口裕之、吉田貞史

n-situ 分光エリプソメータによるSiC 酸化速度の酸素分圧依存性測定
SiC及び関連ワイドギャップ半導体研究会,SiC及び関連ワイドギャップ半導体研究会 第16回講演会 200711
山本健史、土方泰斗、矢口裕之、吉田貞史

SiC 酸化速度の極薄膜厚領域におけるモデル計算
SiC及び関連ワイドギャップ半導体研究会,SiC及び関連ワイドギャップ半導体研究会 第16回講演会 200711
土方泰斗、山本健史、矢口裕之、吉田貞史

分光エリプソメータによるSiO2/SiC界面の光学的評価 -酸化法、面方位依存性-(2)
SiC及び関連ワイドギャップ半導体研究会,SiC及び関連ワイドギャップ半導体研究会 第16回講演会 200711
橋本英樹、土方泰斗、矢口裕之、吉田貞史

Model Calculation of SiC Oxidation Rates in the Thin Oxide Regime
International Conference on Silicon Carbide and Related Materials 2007 200710
Y. Hijikata, T. Yamamoto, H. Yaguchi and S. Yoshida

Oxygen-Partial-Pressure Dependence of SiC Oxidation Rate Studied by In-situ Spectroscopic Ellipsometry
International Conference on Silicon Carbide and Related Materials 2007 200710
T. Yamamoto, Y. Hijikata, H. Yaguchi and S. Yoshida

Improvement of the Surface Morphology of a-Plane InN Using Low-Temperature InN Buffer Layers
7th International Conference on Nitride Semiconductors,Technical Program of the 7th International Conference on Nitride Semiconductors:83 200709
G. Shikata, S. Hirano, T. Inoue, M. Orihara, Y. Hijikata, H. Yaguchi and S. Yoshida

Lattice Polarity Determination for GaN by Modulation Spectroscopy
7th International Conference on Nitride Semiconductors,Technical Program of the 7th International Conference on Nitride Semiconductors:92 200709
R. Katayama, H. Yaguchi, K. Onabe

Photoluminescence of Cubic InN Films on MgO(001) Substrates
7th International Conference on Nitride Semiconductors,Technical Program of the 7th International Conference on Nitride Semiconductors:75 200709
T. Inoue, Y. Iwahashi, S. Oishi, M. Orihara, Y. Hijikata, H. Yaguchi and S. Yoshida

Photoluminescence Study of Hexagonal InN/InGaN Quantum Well Structures Grown on 3C-SiC (001) Substrates by Molecular Beam Epitax
7th International Conference on Nitride Semiconductors,Technical Program of the 7th International Conference on Nitride Semiconductors:75 200709
S. Hirano, T. Inoue, G. Shikata, M. Orihara, Y. Hijikata, H. Yaguchi and S. Yoshida

変調分光法によるGaNの極性評価
第68回応用物理学会学術講演会,第68回応用物理学会学術講演会講演予稿集:391 200709
片山竜二,矢口裕之,尾鍋研太郎

光照射によるGaInAsN混晶の発光効率向上に関する研究
第68回応用物理学会学術講演会,第68回応用物理学会学術講演会講演予稿集:339 200709
谷岡健太郎,遠藤雄太,伊藤正俊,土方泰斗,矢口裕之,吉田貞史,片山竜二,尾鍋研太郎,吉田正裕,秋山英文

窒素をデルタドープしたGaAsにおける単一の等電子トラップからの発光の偏光特性
第68回応用物理学会学術講演会,第68回応用物理学会学術講演会講演予稿集:337 200709
遠藤雄太,伊藤正俊,土方泰斗,矢口裕之,吉田貞史,吉田正裕,秋山英文,中島史博,片山竜二,尾鍋研太郎

窒素をデルタドープしたGaP中の等電子トラップからの発光
第68回応用物理学会学術講演会,第68回応用物理学会学術講演会講演予稿集:337 200709
伊藤正俊,遠藤雄太,土方泰斗,矢口裕之,吉田貞史,吉田正裕,秋山英文,中島史博,片山竜二,尾鍋研太郎

In-situ分光エリプソメ-タによるSiC酸化速度の酸素分圧依存性測定
応用物理学会,第68回応用物理学会学術講演会講演予稿集:425 200709
山本健史,土方泰斗,矢口裕之,吉田貞史

RF-MBE法を用いた4H-SiC基板(0001)面および(000-1)面上へのInGaN成長
第68回応用物理学会学術講演会,第68回応用物理学会学術講演会講演予稿集:370 200709
折原操,四方剛,井上赳,塚越裕介,土方泰斗,矢口裕之,吉田貞史

SiC酸化速度の極薄膜厚領域におけるモデル計算
第68回応用物理学会学術講演会,第68回応用物理学会学術講演会講演予稿集:425 200709
土方泰斗,山本健史,矢口裕之,吉田貞史

分光エリプソメータによるSiO2/SiC界面の光学的評価 -酸化法、面方位依存性-
第68回応用物理学会学術講演会,第68回応用物理学会学術講演会講演予稿集:424 200709
橋本英樹,土方泰斗,矢口裕之,吉田貞史

分光エリプソメトリによるInGaN混晶の光学的特性評価
応用物理学会,第68回応用物理学会学術講演会講演予稿集:362 200709
塚越裕介,折原操,土方泰斗,矢口裕之,吉田貞史,崔成伯,石谷善博,吉川明彦

Twin photoluminescence peaks from single isoelectronic traps in nitrogen delta-doped GaAs
13th International Conference on Modulated Semiconductor Structures,Abstract Book of the 13th International Conference on Modulated Semiconductor Structures:161-163 200707
Y. Endo, Y. Hijikata, H. Yaguchi, S. Yoshida, M. Yoshita, H. Akiyama, F. Nakajima, R. Katayama and K. Onabe

Modulation spectroscopic investigation on lattice polarity of GaN
26th Electronic Materials Symposium,Extended Absctracts of the 26th Electronic Materials Symposium:E9 200707
R. Katayama, H. Yaguchi and K. Onabe

RF-MBE法によるGaNバッファー層を用いたサファイアR面基板上へのA面InNの成長
応用物理学会,第54回応用物理学連合学術講演会:408 200703
四方剛、平野茂、ファリズ・アブドウルラーシッド、平山秀樹、折原操、土方泰斗、矢口裕之、吉田貞史

RF-MBE法を用いた3C-SiC基板上へのInN/InGaN量子井戸構造の作製
応用物理学会,第54回応用物理学連合学術講演会:411 200703
折原操、平野茂、四方剛、井上赳、塚越裕介、土方泰斗、矢口裕之、吉田貞史

RF-MBE法を用いた4H-SiC基板上へのInN/InGaN量子井戸構造の作製(III)
応用物理学会,第54回応用物理学連合学術講演会:412 200703
折原操、平野茂、四方剛、井上赳、塚越裕介、土方泰斗、矢口裕之、吉田貞史

窒素をデルタドープしたGaAsにおける等電子トラップからの発光
応用物理学会,第54回応用物理学連合学術講演会:358 200703
遠藤雄太、土方泰斗、矢口裕之、吉田貞史、吉田正裕、秋山英文、中島史博、片山竜二、尾鍋研太郎

In-situ 分光エリプソメータによるSiC 酸化速度の酸素分圧依存性測定
SiC及び関連ワイドギャップ半導体研究会 第15回講演会 200611
山本健史、土方泰斗、矢口裕之、吉田貞史

テラヘルツ分光法によるSiC エピタキシャル成長膜のキャリヤ濃度、移動度、膜厚の同時評価
SiC及び関連ワイドギャップ半導体研究会 第15回講演会 200611
大石慎吾、土方泰斗、矢口裕之、吉田貞史

窒素イオン注入によりアモルファス化された4H-SiCを用いたMOSキャパシタの作製
SiC及び関連ワイドギャップ半導体研究会 第15回講演会 200611
土方泰斗,矢口裕之,吉田貞史,F.Moscatelli,A.Poggi,S.Solmi,R.Nipoti

分光エリプソメータによるSiO2/SiC界面の光学的評価 -酸化法、面方位依存性-
SiC及び関連ワイドギャップ半導体研究会 第15回講演会 200611
橋本英樹、窪木亮一、土方泰斗、矢口裕之、吉田貞史

分光エリプソメータによるSiO2/SiC界面の光学的評価 -複数の入射角による測定-
SiC及び関連ワイドギャップ半導体研究会 第15回講演会 200611
窪木亮一、橋本英樹、土方泰斗、矢口裕之、吉田貞史

GaN, InN結晶特性からみた立方晶、六方晶の違いに関する考察
日本結晶成長学会,第31回結晶成長討論会 200611
矢口裕之

Structural and Optical Characterization of High In Content Cubic InGaN on GaAs(001) Substrates by RF-MBE
International Workshop on Nitride Semiconductors 2006,International Workshop on Nitride Semiconductors 2006 200610
T. Nakamura, Y, Endo, R. Katayama, H. Yaguchi and K. Onabe

Photoluminescence Study of Isoelectronic Traps in Dilute GaAsN alloys
International Workshop on Nitride Semiconductors 2006,International Workshop on Nitride Semiconductors 2006 200610
H. Yaguchi, T. Aoki, T. Morioke, Y. Hijikata, S. Yoshida, M. Yoshita, H. Akiyama, D. Aoki and K. Onabe

Micro-photoluminescence study on nitrogen atomic-layer doping in GaAs
Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures,Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures:51 200609
H. Yaguchi

RF-MBE growth of a-plane InN on r-plane sapphire with a GaN underlayer
International Conference on Molecular Beam Epitaxy 2006,International Conference on Molecular Beam Epitaxy 2006:137 200609
G. Shikata, S. Hirano, T. Inoue, M. Orihara, Y. Hijikata, H. Yaguchi and S. Yoshida

RF-MBE growth of InN/InGaN quantum well structures on 3C-SiC substrates
International Conference on Molecular Beam Epitaxy 2006,International Conference on Molecular Beam Epitaxy 2006:136 200609
S. Hirano, T. Inoue, G. Shikata, M. Orihara, Y. Hijikata, H. Yaguchi and S. Yoshida

Simultaneous Determination of the Carrier Concentration, Mobility and Thickness of SiC Homo-Epilayers Using Terahertz Reflectance Spectroscopy
European Conference on SiC and Related Materials,European Conference on SiC and Related Materials:13 200609
S. Oishi, Y. Hijikata, H. Yaguchi and S. Yoshida

窒素イオン注入によりアモルファス化された4H-SiCを用いたMOSキャパシタの作製
第67回応用物理学会学術講演会,第67回応用物理学会学術講演会:377 200608
土方泰斗,矢口裕之,吉田貞史,F.Moscatelli,A.Poggi,S.Solmi,R.Nipoti

分光エリプソメータによるSiO2/SiC界面の光学的評価 -酸化法、面方位依存性-
第67回応用物理学会学術講演会,第67回応用物理学会学術講演会:377 200608
橋本英樹、窪木亮一、土方泰斗、矢口裕之、吉田貞史

赤外反射分光法を用いたSiCエピ膜の電気的特性の評価
第67回応用物理学会学術講演会,第67回応用物理学会学術講演会:370 200608
大石慎吾、土方泰斗、矢口裕之、吉田貞史

RF-MBE法により成長した立方晶InNのPL測定
第67回応用物理学会学術講演会,第67回応用物理学会学術講演会:308 200608
井上赳,平野茂,折原操,土方泰斗,矢口裕之,吉田貞史

窒素をδドープしたGaAs における等電子トラップの顕微フォトルミネッセンス測定
第67回応用物理学会学術講演会,第67回応用物理学会学術講演会:293 200608
遠藤雄太、谷岡健太郎、土方泰斗、矢口裕之、吉田貞史、吉田正裕、秋山英文、中島史博、片山竜二、尾鍋研太郎

分光エリプソメトリによる高In組成InGaN の光学的評価
第67回応用物理学会学術講演会,第67回応用物理学会学術講演会:312 200608
塚越裕介,折原操,土方泰斗,矢口裕之,吉田貞史,崔成伯,石谷善博,吉川明彦

Micro-photoluminescence study of nitrogen atomic-layer doped GaAs
25th Electronic Materials Symposium:238-239 200607
Y. Endo, K. Tanioka, Y. Hijikata, H. Yaguchi, S. Yoshida, M. Yoshita, H. Akiyama, W. Ono, F. Nakajima, R. Katayama and K. Onabe

Micro Raman study on the improvement of luminescence efficiency of GaAsN alloys
13th International Conference on Metalorganic Vapor Phase Epitaxy 200605
K. Tanioka, Y. Endo, Y. Hijikata, H. Yaguchi, S. Yoshida, N. Yoshita, H. Akiyama and K. Onabe

Micro-photoluminescence study of nitrogen delta-doped GaAs grown by metalorganic vapor phase epitaxy
13th International Conference on Metalorganic Vapor Phase Epitaxy 200605
Y. Endo, K. Tanioka, Y. Hijikata, H. Yaguchi, S. Yoshida, M. Yoshita, H. Akiyama, W. Ono, F. Nakajima, R. Katayama and K. Onabe

RF-MBE法を用いた立方晶InNの結晶成長(IV)
第53回応用物理学関係連合講演会,第53回応用物理学関係連合講演会 200603
岩橋洋平、折原操、土方泰斗、矢口裕之、吉田貞史

In-situ分光エリプソメータによるSiCの酸化の実時間観察
応用物理学会,第53回応用物理学関係連合講演会 200603
覚張光一、窪木亮一、山本健史、土方泰斗、矢口裕之、吉田貞史

ラマン分光を用いたGaAsN混晶の発光効率向上に関する研究
第53回応用物理学関係連合講演会,第53回応用物理学関係連合講演会 200603
谷岡健太郎、遠藤雄太、土方泰斗、矢口裕之、吉田貞史、青木大一郎、尾鍋研太郎

RF-MBE法を用いた3C-SiC(001)基板上への六方晶InNの結晶成長
応用物理学会,第53回応用物理学関係連合講演会 200603
井上赴、岩橋洋平、平野茂、折原操、土方泰斗、矢口裕之、吉田貞史

RF-MBE法を用いたSiC基板上へのInN/InGaN量子井戸構造の作製
応用物理学会,第53回応用物理学関係連合講演会 200603
折原操、岩橋洋平、平野茂、井上赴、土方泰斗、矢口裕之、吉田貞史

Real-time observation of SiC oxidation using an in situ spectroscopic ellipsometer
2006 Japanese-Spanish-German Joint Workshop on Advanced Semiconductor Optoelectronic Materials and Devices 2006
S. Yoshida, K. Kakubari, Y. Hijikata, H. Yaguchi and M. Yoshikawa

Real Time Observation of SiC Oxidation Using In-Situ Spectroscopic Ellipsometer
International Conference on Silicon Carbide and Related Materials 2005,Final Technical Program:78 200509
K. Kakubari, R. Kuboki, Y. Hijikata, H. Yaguchi and S. Yoshida

Off-Angle Dependence of Characteristics of 4H-SiC-Oxide Interfaces
International Conference on Silicon Carbide and Related Materials 2005,Final Technical Progam:36 200509
Y. Hijikata, H. Yaguchi, S. Yoshida, Y. Takata, K. Kobayashi, H. Nohira and T. Hattori

RF-MBE法を用いた4H-SiC基板上へのInN/InGaN量子井戸構造の作製(II)
応用物理学会,第66回応用物理学会学術講演会 200509
折原操,岩橋洋平,平野茂,土方泰斗,矢口裕之,吉田貞史

RF-MBE法を用いた中間組成InGaN膜上へのInN/InGaN量子井戸構造の作製
応用物理学会,第66回応用物理学会学術講演会 200509
平野茂,岩橋洋平,折原操,土方泰斗,矢口裕之,吉田貞史

ラマン分光を用いたGaAsN混晶の光照射による構造変化の評価
応用物理学会,第66回応用物理学会学術講演会 200509
矢口裕之,清水博史,森桶利和,青木貴嗣,土方泰斗,吉田貞史,宇佐美徳隆,吉田正裕,秋山英文,青木大一郎,尾鍋研太郎

赤外反射分光法を用いたSiCエピ膜の電気的特性の評価
応用物理学会,第66回応用物理学会学術講演会 200509
大石慎吾,土方泰斗,矢口祐之,吉田貞史

低オフ角C面SiC基板上の酸化膜の評価
応用物理学会,第66回応用物理学会学術講演会 200509
土方泰斗,矢口裕之,吉田貞史,高田恭孝,小林啓介,野平博司,服部健雄

分光エリプソメータによるSiO2/SiC界面の光学的評価 -紫外領域への拡張-
応用物理学会,第66回応用物理学会学術講演会 200509
窪木亮一,覚張光一,土方泰斗,矢口裕之,吉田貞史

RF-MBE growth of cubic InN films on MgO (001) substrates
6th International Conference on Nitride Semiconductors 200508
Y. Iwahashi, A. Nishimoto, M. Orihara, Y. Hijikata, H. Yaguchi and S. Yoshida

Photo-induced improvement of radiative efficiency and structural changes in GaAsN alloys
6th International Conference on Nitride Semiconductors 200508
H. Yaguchi, T. Morioke, T. Aoki, H. Shimizu, Y. Hijikata, S. Yoshida, M. Yoshita, H. Akiyama, N. Usami, D. Aoki and K. Onabe

In situ エリプソメータによるSiCの酸化の実時間観察
応用物理学会,第52回応用物理学関係連合講演会講演予稿集,1:453-453 200504
覚張光一、窪木亮一、土方泰斗、矢口裕之、吉田貞史

様々な傾斜角を有するSiC基板上の酸化膜の評価
応用物理学会,第52回応用物理学関係連合講演会講演予稿集,1:454-454 200504
土方泰斗、矢口裕之、吉田貞史、高田恭孝、小林啓介、野平博司、服部健雄

赤外反射分光法を用いたSiCエピ膜の電気的特性の評価
応用物理学会,第52回応用物理学関係連合講演会講演予稿集,1:448-448 200503
大石慎吾、土方泰斗、矢口裕之、吉田貞史

RF-MBE法を用いた4H-SiC基板上へのInN/InGaN量子井戸構造の作製
応用物理学会,第52回応用物理学関係連合講演会講演予稿集,1:384-384 200503
折原操、北村芳広、岩橋洋平、平野茂、土方泰斗、矢口裕之、吉田貞史

In-situ エリプソメータによるSiC の酸化の実時間観察
SiC及び関連ワイドギャップ半導体研究会 第14回講演会 2005
覚張光一、窪木亮一、土方泰斗、矢口裕之、吉田貞史

赤外反射分光法を用いたSiCエピ膜の電気的特性の評価
SiC及び関連ワイドギャップ半導体研究会 第14回講演会 2005
大石慎吾、土方泰斗、矢口裕之、吉田貞史

分光エリプソメータによるSiO2/SiC界面の光学的評価 -紫外領域への拡張-
SiC及び関連ワイドギャップ半導体研究会 第14回講演会 2005
窪木亮一、覚張光一、橋本英樹、土方泰斗、矢口裕之、吉田貞史

高エネルギー分解能光電子分光による4H-SiC(000-1)面上酸化膜の評価
応用物理学会SiC及び関連ワイドギャップ半導体研究会,SiC及び関連ワイドギャップ半導体研究会第13回講演会予稿集:129-129 200410
土方泰斗、矢口裕之、吉田貞史、高田恭孝、小林啓介、辛埴、野平博司、服部健雄

分光エリプソメータによるSiCの初期酸化過程の観察
応用物理学会SiC及び関連ワイドギャップ半導体研究会,SiC及び関連ワイドギャップ半導体研究会第13回講演会予稿集:127-127 200410
覚張光一、土方泰斗、矢口裕之、吉田貞史

Epitaxial Growth of Hexagonal and Cubic InN Films by Gas Source Molecular Beam Epitaxy
7th China-Japan Symposium on Thin Films,Proceedings of 7th China-Japan Symposium on Thin Films:11-14 200409
S. Yoshida, Y. Kitamura, Y. Iwahashi, H. Tada, M. Orihara, Y. Hijikata and H. Yaguchi

分光エリプソメータによるSiC酸化膜の初期酸化過程の観察(IV)
応用物理学会,第65回応用物理学会学術講演会講演予稿集,1:329-329 200409
覚張光一、土方泰斗、矢口裕之、吉田貞史

RF-MBE法を用いた4H-SiC(0001)基板上へのInNの結晶成長
応用物理学会,第65回応用物理学科学術講演会講演予稿集,1:301-301 200409
北村芳広、岩橋洋平、多田宏之、折原操、土方泰斗、矢口裕之、吉田貞史

ラマン散乱分光法によるInAsN混晶の評価
応用物理学会,第65回応用物理学会学術講演会講演予稿集,1:308-308 200409
本村寛、土方泰斗,矢口裕之、吉田貞史、飛田聡、西尾晋、片山竜二、尾鍋研太郎

レーザ照射によるGaAsN混晶の発光効率向上の窒素濃度依存性
応用物理学会,第65回応用物理学会学術講演会講演予稿集,1:308-308 200409
森桶利和、青木貴嗣、呉智元、吉田正裕、秋山英文、土方泰斗、矢口裕之、吉田貞史、青木大一郎、尾鍋研太郎

低窒素濃度GaPN混晶のフォトルミネッセンス
応用物理学会,第65回応用物理学会学術講演会講演予稿集,1:309-309 200409
青木貴嗣、森桶利和、土方泰斗、矢口裕之、吉田貞史、張保平、三吉靖郎、尾鍋研太郎

RF-MBE法によるMgO(001)基板上への立方晶GaNの成長
応用物理学会,第65回応用物理学会学術講演会講演予稿集,1:290-290 200409
多田宏之、北村芳広、岩橋洋平、折原操、土方泰斗、矢口裕之、吉田貞史

RF-MBE法を用いた4H-SiC基板上へのInGaN結晶成長
応用物理学会,第65回応用物理学会学術講演会講演予稿集,1:301-301 200409
折原操、北村芳広、岩橋洋平、多田宏之、土方泰斗,矢口裕之、吉田貞史

RF-MBE法を用いた立方晶InNの結晶成長(III)
応用物理学会,第65回応用物理学会学術講演会講演予稿集,1:299-299 200409
岩橋洋平、北村芳広、多田宏之、折原操、土方泰斗、矢口裕之、吉田貞史

Characterization of Oxide Films on SiC Epitaxial (000-1) Faces by Angle-Resolved Photoemission Spectroscopic Measurements using Synchrotron Radiation
5th European Conference on Silicon Carbide and Related Materials 200409
Y. Hijikata, H. Yaguchi, S. Yoshida, Y. Takata, K. Kobayashi, S. Shin, H. Nohira and T. Hattori

Growth of high-quality hexagonal InN on 3C-SiC (001) by molecular beam epitaxy
International Workshop on Nitride Semiconductors,International Workshop on Nitride Semiconductors Program & Abstract Book:71-71 200407
H. Yaguchi, Y. Kitamura, K. Nishida, Y. Iwahashi, Y. Hijikata and S. Yoshida

窒素をδドープしたGaAsの顕微フォトルミネッセンス
応用物理学会,第52回応用物理学関係連合講演会講演予稿集,1:394-394 200403
花島君俊、森桶利和、青木貴嗣、土方泰斗、矢口裕之、吉田貞史、吉田正裕、秋山英文、平山琢、片山竜二、尾鍋研太郎

Characterization of oxide films on SiC by spectroscopic ellipsometer
,Extended Abstracts of 1st International Workshop on Ultra-Low-Loss Power Device Technology:203-204 2000
T. Iida, Y. Tomioka, K. Matsunaka, Y. Hijikata, H. Yaguchi, M. Yoshikawa, Y. Ishida, H. Okumura and S. Yoshida

Built-in Electric Field Strength in InP/n+-InP Determined by Photoellipsometry and Photoreflectance
,Extended Abstracts of the 1996 International Conference on Solid State Devices and Materials:724-726 1996
Y-M. Xiong, T. Saitoh, H. Yaguchi and Y. Shiraki
Built-in electric field strength in InP/n+-InP was evaluated by photoellipsometry (PE) and photoreflectance (PR), respectively. Two samples were investigated, each having an undoped (100) InP layer of thickness L (L=100 and 150 nm, respectively) epitaxially grown on top of a heavily doped n-type (100) InP substrate. The measured PE spectra were analyzed using the Franz-Keldysh (FK) theory, taking into account the photovoltage effect induced by the pump beam illumination and the broadening effects due to free-carrier scattering. The PR spectra measured under the low pump beam illumination, on the other hand, were analyzed using the asymptonic form of an Airy function for the FK oscillations. The results of our analysis show good agreement between the field strengths determined by PE and PR, respectively, for each sample investigated, which in turn demonstrates the effectiveness of the tow methods in the characterization of the chosen samples.

The in Situ Growth of Lateral Confinement Enhanced Rectangular AlGaAs/AlAs Quantum Wires by Utilizing the Spontaneous Vertical Quantum Wells
,Extended Abstracts of the 1995 International Conference on Solid State Devices and Materials:737-739 1995
W. Pan, H. Yaguchi, K. Onabe, R. Ito, N. Usami and Y. Shiraki
A proposal for the in situ growth of a lateral confinement enhanced AlGaAs/AlAs quantum wire (QWR) structure, which utilizes the Ga-rich AlGaAs spontaneous vertical quantum wells (SVQWs) formed in the growth of the AlGaAs epilayer in the V-grooves, has been put forward. The actual AlGaAs/AlAs QWR structures have been grown on the V-grooved substrates by low-pressure metalorganic vapor phase epitaxy (MOVPE), and been studied by transmission electron microscope (TEM) observations, photoluminescence (PL) and cathodoluminescence (CL) measurements.

Photoreflectance and Photoluminescence Study of Direct- and Indirect-Gap Band Lineups of GaAsP/GaP Strained Quantum Wells
,Extended Abstracts of the 1994 International Conference on Solid State Devices and Materials:108-110 1994
H. Yaguchi, S. Hashimoto, T. Sugita, Y. Hara, K. Onabe, Y. Shiraki and R. Ito
We study the direct- and indirect-gap band lineups of GaAsP/GaP strained quantum wells by the combination of photoreflectance (PR) and photoluminescence (PL) spectroscopy. From the comparison between the transition energies obtained by the PR measurements and those calculated base don the envelope function approximation including the effect of the spin-orbit split-off bands, the conduction band offset ratio is estimated to be 0.60 + or - 0.04 at the Gamma point. This leads to a type-I band lineup at the X point, where the conduction band offset ratio is 0.44 + or - 0.06. The PL results are in good agreement qualitatively and quantitatively with this band lineup.

Characterization of Interface Roughness in Ge/SiGe Heterostructures Using Photoreflectance Spectroscopy
,Extended Abstracts of the 1993 International Conference on Solid State Devices and Materials:910-912 1993
H. Yaguchi, K. Tai, K. Takemasa, K. Onabe, Y. Shiraki and R. Ito
We have investigated Ge/SiGe strained-barrier quantum well (SBQW) structures using photoreflectance (PR) spectroscopy. On the basis of transition energies related to the quantum well formed at the Gamma point, band offsets at the Ge/SiGe heterojunction was found to vary linearly with germanium composition in the SiGe layer. Conduction band offset ratio Qc (= Delta Ec/(Delta Ec + Delta Evh)) at the Gamma point was evaluated to be 0.68 + or - 0.08. From the intrinsic linewidth of the optical transitions, interface roughness at the Ge/SiGe heterointerface was characterized for the first time and estimated to be one monolayer (ML). In addition, the splittings in PR spectra were observed in some samples at low temperatures. These splittings were due to the difference in the well width and corresponded to the height (or depth) of about 10 ML.

MOVPE Selective Growth of Cubic GaN in Small Areas on Patterned GaAs(100) Substrates
,Extended Abstracts of the 1993 International Conference on Solid State Devices and Materials:113-115 1993
M. Nagahara, S. Miyoshi, H. Yaguchi, K. Onabe, Y. Shiraki and R. Ito

Photoreflectance study of GaAs/GaAsP strained-barrier quantum well structures
,Extended Abstracts of the 1992 International Conference on Solid State Devices and Materials:589-591 1992
H. Yaguchi, X. Zhang, K. Onabe, Y. Shiraki and R. Ito
GaAsP strained-layer quantum well structures grown by metalorganic vapor phase epitaxy have been investigated using photoreflectance spectroscopy. The authors have focused their attention on GaAs/GaAsP 'strained-barrier' quantum well structures on GaAs (100) substrates. They have determined the band offset at the heterojunction and its dependence on the phosphorus composition. It was found that the band offsets are almost linearly dependent on the phosphorus composition in the range of x<or=0.23. In addition, it was derived that the conduction band offset ratio Qc=0.57+or-0.05.

Structural Characterization of Si/Ge Heterointerfaces by Secondary Ion Mass Spectroscopy
,4th International Conference on Molecular Beam Epitaxy 199104
S. Fukatsu, H. Yaguchi, K. Fujita,Y. Shiraki and R.Ito

HBO2ソースによるGe中のBのdelta-ドーピング
,応用物理学会第38回連合講演会 199103
矢口裕之,五十嵐孝行,藤田研,深津晋,白木靖寛,伊藤良一

MBE法により形成されたシリコン表面の初期酸化
,応用物理学会第38回連合講演会 199103
五十嵐孝行,田村佳哉,矢口裕之,藤田研,深津晋,服部健雄,白木靖寛,伊藤良一

SbによるGeの表面偏析抑制の機構
,応用物理学会第38回連合講演会 199103
藤田研,深津晋,矢口裕之,五十嵐孝行,白木靖寛,伊藤良一

Si MBEにおけるGeの表面偏析の解析
,応用物理学会第38回連合講演会 199103
深津晋,藤田研,矢口裕之,白木靖寛,伊藤良一

Si1-xGex/Siエピタキシャル膜中のミスフィット転位の上昇運動のその場観察
,応用物理学会第38回連合講演会 199103
山下善文,目良裕,前田康二,矢口裕之,藤田研,白木靖寛

SIMSを用いたSiGe界面における急峻性評価
,応用物理学会第38回連合講演会 199103
深津晋,藤田研,矢口裕之,白木靖寛,伊藤良一

SbによるSi/Ge界面ミキシングの抑制
応用物理学会,応用物理学会第51回講演会 199009
藤田研,深津晋,矢口裕之,五十嵐孝行,張保平,白木靖寛,伊藤良一

Si1-xGex歪薄膜の熱処理による歪の緩和
応用物理学会,応用物理学会第51回講演会 199009
矢口裕之,張保平,藤田研,深津晋,白木靖寛,伊藤良一

Suppression of Interfacial Mixing in Si/Ge Superlattices by Sb Deposition
,22nd Conference on Solid State Devices and Materials 199008
K. Fujita, S. Fukatsu, H. Yaguchi, T. Igarashi, Y. Shiraki and R. Ito

原子レベルで平坦なシリコン上の酸化膜形成とその構造
応用物理学会,応用物理学関連講演会 199003
五十嵐孝行,高瀬和彦,服部健雄,矢口裕之,藤田研,深津晋,白木靖寛

Pb/Si(111)表面超構造のRHEEDによる観察
,第7回表面科学講演大会 198712
矢口裕之,馬場茂,金原粲

RHEEDによるPb/Si(111)表面超構造の研究
,第28回真空に関する連合講演会 198711
矢口裕之,馬場茂,金原粲

RHEED Study of Superstructures of Submonolayer Lead Films on Silicon(111) Surfaces
,4th Int. Conf. Solid Films and Surfaces 198708
H. Yaguchi, S. Baba and A. Kinbara

その他
局所ドーピング構造半導体による単一光子発生
埼玉大学総合研究機構,総合研究機構研究プロジェクト研究成果報告書,第6号(平成19年度) 200809
矢口裕之

等電子トラップを利用した単一光子発生素子の作製
,科学研究費補助金(基盤研究(c))研究成果報告書,平成17-18年度 200703
矢口裕之,吉田貞史,土方泰斗

SiCパワーデバイスの実用化に向けて
埼玉大学総合研究機構地域共同研究センター,第1回テクノ・カフェ : セミナー資料:1-6 200702
矢口裕之

窒化物半導体材料評価のための顕微変調分光システムの開発
埼玉大学総合研究機構,総合研究機構研究プロジェクト研究成果報告書,第5号(18年度):561-562 2007
矢口裕之
Development of micro-modulation spectroscopy system for the characterization of nitride semiconductors

InN/InGaN 系結晶の基礎物性解明および結晶成長のための基板探索 : RF-MBE 法によるサファイアR 面基板上へのA 面InN の結晶成長
埼玉大学総合研究機構地域共同研究センター産学連携推進部門,埼玉大学地域共同研究センター紀要,8:48-51 2007
吉田貞史,矢口裕之,折原操
The improvement of the surface morphology of a-plane InN films grown by RF molecular beam epitaxy is reported. Using low-temperature (LT) InN buffer layers, we could successfully obtain InN films with a smooth surface. The full width at half maximum of the x-ray diffraction (11-20) rocking curve along the [0001] InN direction was 2200 arcsec for a-plane InN samples grown at 450°C with a LT-InN buffer layer. Thus, we could improve also the crystalline quality of a-plane InN films by using LT-InN buffer layers. We observed strong polarization anisotropy in the photoluminescence spectra of a-plane InN, which is typical of nonpolar wurtzite III-nitride films.
InN, molecular beam epitaxy, nonpolar, photoluminescence

InN/InGaN 系結晶の基礎物性解明および結晶成長のための基板探索 : RF-MBE 法によるサファイアR 面基板上へのA 面InN の結晶成長
埼玉大学総合研究機構地域共同研究センター産学連携推進部門,埼玉大学地域共同研究センター紀要,8:48-51 2007
吉田貞史,矢口裕之,折原操
RF-MBE Growth of a-plane InN on r-plane sapphire substrates

極低窒素濃度化合物半導体混晶におけるアイソエレクトロニックトラップによる発光に関する研究<研究成果報告>
埼玉大学工学部,埼玉大学紀要, 工学部, 第1部論文集,39:131-132 200607
矢口裕之,青木貴嗣

先端物質によるフロンティアフォトニクス<研究成果報告>
埼玉大学工学部,埼玉大学紀要, 工学部, 第1部論文集,39:138-142 200607
鎌田憲彦,明連広昭,矢口裕之,谷口弘三

InN/InGaN系結晶の基礎物性解明および結晶成長のための基板探索
埼玉大学総合研究機構地域共同研究センター産学連携推進部門,埼玉大学地域共同研究センター紀要,7:63-63 2006
吉田貞史,矢口裕之,折原操

RF-MBE法を用いたMgO(001)基板上への立方晶InN薄膜の成長
埼玉大学総合研究機構地域共同研究センター産学連携推進部門,埼玉大学地域共同研究センター紀要,6:71-71 2005
吉田貞史,矢口裕之,折原操

特許等知的財産

登録済特許
多孔質酸化チタン薄膜とその製造方法 , 2003-321222

研究費

科学研究費補助金(研究代表者)
2012-2014 , 局所ドーピング構造半導体による量子相関光子の生成および制御 , 基盤研究(B)
2009-2011 , 局所ドーピング構造半導体による単一光子発生に関する研究 , 基盤研究B
2005-2006 , 等電子トラップを利用した単一光子発生素子の作製 , 基盤研究(C)
科学研究費補助金(研究分担者)
2013-2017 , 非熱平衡状態フォノン輸送制御による半導体光素子の新展開 , 基盤研究(B)
2009-2010 , 有機N原料によるInNおよび関連混晶薄膜のMOVPE成長 , 特定領域研究
2007-2009 , 狭バンドギャップIII-V-N混晶半導体量子ナノ構造の作製と物性応用 , 基盤研究(B)

研究諸活動

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, 応用物理学会

教育活動実績

授業等

前期 , 固体物性論(工学部)
後期 , 基礎電子回路(工学部)
前期 , 線形代数I(工学部)
後期 , 電気電子システム実験3(工学部)
前期 , 光エレクトロニクス物性特論(院・理工学前期)
後期 , 光エレクトロニクス物性特論(院・理工学後期)

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