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.
Papers
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Journal ArticleDOI
Repeated temperature modulation epitaxy for p-type doping and light-emitting diode based on ZnO
Atsushi Tsukazaki,Akira Ohtomo,Takeyoshi Onuma,M. Ohtani,Takayuki Makino,Masatomo Sumiya,Keita Ohtani,Shigefusa F. Chichibu,S. Fuke,Yusaburou Segawa,Hideo Ohno,Hideomi Koinuma,Masashi Kawasaki +12 more
TL;DR: In this paper, the authors used a new technique to fabricate p-type ZnO reproducibly, and showed high-quality undoped films with electron mobility exceeding that in the bulk.
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Origin of defect-insensitive emission probability in In-containing (Al,In,Ga)N alloy semiconductors.
Shigefusa F. Chichibu,Akira Uedono,Akira Uedono,Takeyoshi Onuma,Benjamin A. Haskell,Arpan Chakraborty,T. Koyama,Paul T. Fini,Stacia Keller,Steven P. DenBaars,James S. Speck,Umesh K. Mishra,Shuji Nakamura,Shigeo Yamaguchi,Shigeo Yamaguchi,Satoshi Kamiyama,Hiroshi Amano,Isamu Akasaki,Jung Han,Takayuki Sota +19 more
TL;DR: Here it is explained why In-containing (Al,In,Ga)N bulk films exhibit a defect-insensitive emission probability, and it is concluded that localizing valence states associated with atomic condensates of In–N preferentially capture holes, which have a positive charge similar to positrons.
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Nitrogen doped MgxZn1−xO/ZnO single heterostructure ultraviolet light-emitting diodes on ZnO substrates
Ken Nakahara,Shunsuke Akasaka,Hiroyuki Yuji,Kentaro Tamura,Tetsuo Fujii,Yoshio Nishimoto,Daiju Takamizu,Atsushi Sasaki,Tetsuhiro Tanabe,Hidemi Takasu,H. Amaike,Takeyoshi Onuma,Shigefusa F. Chichibu,Atsushi Tsukazaki,Akira Ohtomo,Masashi Kawasaki +15 more
TL;DR: In this paper, the authors have grown nitrogen-doped MgxZn1−xO:N films on Zn-polar ZnO single crystal substrates by molecular beam epitaxy.
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Limiting factors of room-temperature nonradiative photoluminescence lifetime in polar and nonpolar GaN studied by time-resolved photoluminescence and slow positron annihilation techniques
Shigefusa F. Chichibu,Akira Uedono,Akira Uedono,Takeyoshi Onuma,T. Sota,Benjamin A. Haskell,Steven P. DenBaars,James S. Speck,Shuji Nakamura +8 more
TL;DR: In this article, the authors show that the nonradiative recombination process is governed not by single point defects, but by certain defects introduced with the incorporation of VGa, such as VGa-defect complexes.
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Improvements in quantum efficiency of excitonic emissions in ZnO epilayers by the elimination of point defects
Shigefusa F. Chichibu,Takeyoshi Onuma,Masashi Kubota,Akira Uedono,Akira Uedono,T. Sota,Atsushi Tsukazaki,Akira Ohtomo,Masashi Kawasaki +8 more
TL;DR: In this article, the internal quantum efficiency of the near-band-edge excitonic photoluminescence (PL) in ZnO epilayers was significantly improved by eliminating point defects, as well as by the use of HITAB on a ScAlMgO4 substrate as epitaxial templates.