通过作者查论文: Hajime Okumura

文章题目页数

作者: Tetsuo Takahashi, Yuuki Ishida, Hajime Okumura, Sadafumi Yoshida, Toshihiro Sekigawa
207
作者: Mitsuaki Shimizu, H. Ohkita, Akira Suzuki, Hajime Okumura
1465
作者: Mitsuaki Shimizu, Hiroshi Chonan, Guaxi Piao, Hajime Okumura, Hisayuki Nakanishi
摘要: In order to improve the crystal quality of MBE-grown GaN layers we employed a high temperature growth process and enhanced the lateral overgrowth. The grain size of the GaN layer was enlarged up to 2 "m in diameter. Significant improvement in the XRD characteristics was found, and the FWHM value of the asymmetric (10-12) XRD ω-scan peak became less than 400 arcsec when the layer thickness was 3 "m. Further, to planarise the surface, the low temperature gallium-rich growth process was employed and the large grooves between the grains vanished.
1493
作者: Hajime Okumura, H. Hamaguchi, Kazushi Ohta, G. Feuillet, Krishnan Balakrishnan, Yuuki Ishida, Shigefusa F. Chichibu, Hachiro Nakanishi, Takao Nagatomo, Sadafumi Yoshida
1167
作者: Toshihide Ide, Mitsuaki Shimizu, Akira Suzuki, Xu-Qiang Shen, Hajime Okumura, Toshio Nemoto
1519
作者: Yuuki Ishida, Tetsuo Takahashi, Hajime Okumura, Toshihiro Sekigawa, Sadafumi Yoshida
253
作者: Keiko Masumoto, Kazutoshi Kojima, Hajime Okumura
摘要: We grew epitaxial layers on 3-inch epitaxial wafers with a vicinal off-angle, using a horizontal hot-wall chemical vapor deposition system that had a reactor capacity of 3 x 150 mm. Uniformity (σ/mean) of thickness and carrier concentration as small as 1.7% and 5.6%, respectively, were successfully obtained. We succeeded in decreasing triangular surface defects and polytype inclusions by increasing the growth temperature and lowering the C/Si ratio. In addition, I-V characteristics of Schottky barrier diodes on an epitaxial layer showed that a high blocking voltage of 960 V and a low leakage current of less than 1 x 10-6 A/cm2 were obtained with a yield of 78%.
193
作者: Yuuki Ishida, Tetsuo Takahashi, Hajime Okumura, Tamotsu Jikimoto, Hidekazu Tsuchida, Masahito Yoshikawa, Yuichi Tomioka, M. Midorikawa, Yasuto Hijikata, Sadafumi Yoshida
1013
作者: Junji Senzaki, Atsushi Shimozato, Kazutoshi Kojima, Shinsuke Harada, Keiko Ariyoshi, Takahito Kojima, Yasunori Tanaka, Hajime Okumura
摘要: Threshold voltage (VTH) of SiC-MOSFETs on various crystal faces has been investigated systematically using the same bias-temperature-stress (BTS) conditions. In addition, dependences of gate-oxide-forming process on VTH instability is also discussed. Nitridation treatments such as N2O and NH3 post-oxidation annealing (POA) are effective in stabilization of VTH under both positive-and negative-BTS tests regardless of crystal face. On the other hand, serious VTH instability was confirmed in MOSFETs with gate oxide by pyrogenic oxidation followed by H2 POA.
521
作者: Satoshi Tanimoto, Masanori Miyabe, Takamitsu Shiiyama, Tatsuhiro Suzuki, Hiroshi Yamaguchi, Shinichi Nakashima, Hajime Okumura
摘要: There is still little consensus regarding why low contact resistivity is achieved when Ni on n-type 4H- and 6H-SiC is annealed at temperatures of more than above 950°C. The objective of this paper is to provide an answer concerning to this question. It is has been reported that even Ni-based contacts formed in the n++ region exhibited a steep reduction of contact resistivity in an annealing temperature range > 900°C. This effect reduction cannot be explained by the carbon vacancy induced donor model (Vc model) proposed by Han and his coworkers [Appl. Phys. Lett., Vol. 79, p. 1816 (2001)]. And, it is clarified that It was observed that the surface of substrates annealed at 1000°C was not covered with not Ni2Si but with a thin layer of NiSi. Finally, a plausible model is proposed that as the result of annealing at higher temperatures, results in the formation of the a NiSi/SiC system is builtat the substrate interface, resulting in significant reduction in low causing contact resistivity to be reduced significantly.
465
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