Papers by Author: Shinichi Nakashima

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Authors: Eiji Kurimoto, Hiroshi Harima, Tadao Toda, Minoru Sawada, Shinichi Nakashima, Motohiro Iwami
Authors: Eiji Kurimoto, M. Hangyo, Hiroshi Harima, Kenji Kisoda, Taro Nishiguchi, Shigehiro Nishino, Shinichi Nakashima, Masakazu Katsuno, Noboru Ohtani
Authors: Takeshi Mitani, Shinichi Nakashima, Masaru Tomobe, Shi Yang Ji, Kazutoshi Kojima, Hajime Okumura
Abstract: We have investigated Raman spectra of p-type 4H-SiC crystals with hole concentration ranging from 3×1016 to 1×1021 cm-3. For folded transverse acoustic (FTA) doublet modes, Fano interference profiles were analyzed, and the frequency shift due to Fano interference was obtained as a function of hole concentration. We demonstrated that the shift of the FTA doublet modes is a quantitative measure for evaluating of hole concentration of p-type 4H-SiC. Spectral features of transverse optical (TO) and longitudinal optical phonon-plasmon coupled (LOPC) modes were also studied for various carrier concentrations. The results show that the full width at half maximum of the LOPC and relative intensity of TO and the LOPC can be used as other calibration measures for hole concentration.
Authors: Hiroshi Harima, Toru Hosoda, Shinichi Nakashima
Authors: K. Narita, Yasuto Hijikata, Hiroyuki Yaguchi, Sadafumi Yoshida, Junji Senzaki, Shinichi Nakashima
Authors: T. Kitamura, Shinichi Nakashima, Tomohisa Kato, K. Kojima, Hajime Okumura
Abstract: We characterized the 4H- and 6H-SiC bulk crystals with graded doping and epitaxial films with various carrier densities by Raman scattering spectroscopy. Electrical properties such as free carrier density were examined for the SiC crystals through Raman measurements of the A1 LO-phonon plasmon coupled (LOPC) mode and its line shape analysis. The peak frequency and band width of LOPC mode varied with carrier density in the range from 1016 to 1019 cm-3. The line shape analysis revealed that the carrier density in the SiC crystals can be simply estimated from measured frequency shift of LOPC mode for 4H- and 6H-SiC crystals.
Authors: Shinichi Nakashima, Takeshi Mitani
Abstract: Raman spectroscopy using deep UV (DUV) light excitation has been applied to characterizing process-induced defects in surface layers in SiC. Raman spectra of P+-ion implanted and post annealed SiC have been measured as a function of dose level and annealing temperature. The recovery of the crystallinity and electrical activity have been evaluated. Precipitation of excess phosphorus was found in heavily doped specimens. High dose implanted and post annealed samples show uneven distribution of residual defects, which is demonstrated by mapping of Raman bandwidth. Damage in 4H-SiC surfaces, which were mechanically polished with various sizes of abrasives, has been evaluated from DUV micro-Raman measurements. The Raman analysis demonstrates that bandwidth and peak frequency can be used as monitors of the polish–induced damage. It is found that localized defects reducing free carrier density remain even after polishing with small sized abrasives.
Authors: Yoshimitsu Yamada, Shin Ichi Nishizawa, Shinichi Nakashima, Kazuo Arai
Authors: Yoshimitsu Yamada, Kazukiyo Sagawa, Shinichi Nakashima
Authors: Mitsuo Okamoto, Ryouji Kosugi, Shinichi Nakashima, Kenji Fukuda, Kazuo Arai
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