T
Takeyoshi Onuma
Researcher at University of Tsukuba
Publications - 57
Citations - 4390
Takeyoshi Onuma is an academic researcher from University of Tsukuba. The author has contributed to research in topics: Photoluminescence & Epitaxy. The author has an hindex of 25, co-authored 52 publications receiving 4210 citations.
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Journal ArticleDOI
Photoluminescence and positron annihilation studies on Mg-doped nitrogen-polarity semipolar (101¯1¯) GaN heteroepitaxial layers grown by metalorganic vapor phase epitaxy
Takeyoshi Onuma,Akira Uedono,Hirokuni Asamizu,Hitoshi Sato,John F. Kaeding,Michael Iza,S. P. DenBaars,Shuji Nakamura,S. F. Chichibu +8 more
TL;DR: In this article, the influence of enhanced stacking fault (SF) formation and lattice-mismatched semipolar heteroepitaxy on the electrical properties of (101¯1¯) Mg-doped GaN epilayers was investigated.
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Reduction of point defect density in cubic GaN epilayers on (001) GaAs substrates using AlxGa1-xN/GaN superlattice underlayers
Shigefusa F. Chichibu,Mutsumi Sugiyama,T. Nozaka,T. Suzuki,Takeyoshi Onuma,Kiyomi Nakajima,T. Aoyama,Masatomo Sumiya,Toyohiro Chikyow,Akira Uedono,Akira Uedono +10 more
TL;DR: In this paper, the effects of Al x Ga 1-x N/GaN superlattice insertion on the structural homogeneity, photoluminescence (PL) lifetime, and defect densities were studied in cubic (c-) GaN epilayers on (001) GaAs substrates grown by low-pressure metalorganic vapor-phase epitaxy.
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Impacts of anisotropic tilt mosaics of state-of-the-art m-plane freestanding GaN substrates on the structural and luminescent properties of m-plane AlxGa1−xN epilayers
TL;DR: In this article, the structural and luminescent properties of m-plane AlxGa1−xN epilayers are analyzed using cross-sectional transmission-electron microscopy and transmissionelectron diffraction analyses.
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Critical Roles of Decomposition-Shielding Layer Deposited at Low Temperature Governing the Structural and Photoluminescence Properties of Cubic GaN Epilayers Grown on (001) GaAs by Metalorganic Vapor Phase Epitaxy
Mutsumi Sugiyama,Taiki Nosaka,Takeyoshi Onuma,Kiyomi Nakajima,Parhat Ahmet,T. Aoyama,Toyohiro Chikyow,Toyohiro Chikyow,Shigefusa F. Chichibu +8 more
TL;DR: In this article, the role of a thin GaN layer deposited at low temperature (LT-GaN) on (001) GaAs substrates during metalorganic vapor phase epitaxy of cubic (c-) GaN were investigated in terms of crystallographic tilt, photoluminescence (PL) line width, and PL lifetime at room temperature.
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Recombination Dynamics of Localized Excitons in Cubic Phase InxGa1—xN/GaN Multiple Quantum Wells on 3C-SiC/Si (001)
Sf. Chichibu,Takeyoshi Onuma,T. Kitamura,Takayuki Sota,S. P. DenBaars,Shuji Nakamura,Hajime Okumura +6 more
TL;DR: In this paper, the authors studied the recombination dynamics of localized excitons in In x Ga 1-x N/c-GaN multiple quantum wells (MQWs) and showed that the spontaneous emission is due to the radiative recombination of exciton localized in disordered quantum nanostructures even at 300 K.