Masaaki Kuzuhara

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057 We report high-resolution (0.07 arcsec) near-infrared polarized intensity images of the circumstellar disk around the star 2MASS J16042165-2130284 obtained with HiCIAO mounted on the Subaru 8.2 m telescope [1]. We present our H-band data, which clearly exhibits a resolved, face-on disk with a large inner hole for the first time at infrared wavelengths(More)
  • M Hatano, N Kunishio, H Chikaoka, J Yamazaki, Z B Makhzani, N Yafune +5 others
  • 2010
AlGaN-channel high-electron mobility transistors (HEMTs) on an AlN substrate have been fabricated for the first time. A maximum saturation current of 0.13A/mm at V GS =2V and a maximum transconductance of 25mS/mm were obtained. DC characteristics of AlGaN-channel HEMT and GaN-channel HEMT were comparatively examined at temperatures ranging from RT to 300ºC.(More)
This paper describes experimental results on the correlation between current collapse and electroluminescence observed under high drain bias conditions in AlGaN/GaN HEMTs with high breakdown voltages over 1000 V. The electroluminescence characteristics were categorized into 2 groups: one from the drain edge with a strong white-appearance emission and the(More)
  • N Yafune, S Hashimoto, K Akita, Y Yamamoto, H Tokuda, M Kuzuhara
  • 2014
We demonstrate an AlN/AlGaN high-electron-mobility transistor (HEMT) fabricated on a free-standing AlN substrate. A metal stack, composed of Zr/Al/Mo/Au, was found to show low contact resistivity for source and drain ohmic contacts. The fabricated AlN/AlGaN HEMT exhibited a maximum drain current of 38 mA/mm with a threshold voltage of-3.4 V. Negligible(More)
Present status and perspective of GaN-based technology in Japan have been presented. An AlGaN/GaN HEMT is expanding its application field from L to W bands and it will replace the Si and GaAs based power amplifiers used in mobile phone base stations, terrestrial/satellite microwave communication systems, and collision avoidance car radar systems. A(More)
Hall electron mobility ͑␮ H ͒ and sheet concentration ͑n s ͒ in AlGaN/GaN heterostructures have been measured from 77 to 1020 K. The effect of the deposited Al 2 O 3 layer is also investigated with varying its thickness. It is found that ␮ H decreases monotonously with the temperature ͑T͒ and its dependence is well approximated with the function of ␮ H =(More)
SUMMARY We have evaluated the tunneling contact resistivity based on numerical calculation of tunneling current density across an AlGaN barrier layer in non-polar AlGaN/GaN heterostructures. In order to reduce the tunneling contact resistivity, we have introduced an n +-Al X Ga 1−X N layer between an n +-GaN cap layer and an i-AlGaN barrier layer. The(More)
A questionnaire about convulsions and other adverse events after vaccination was sent to doctors who administered a diphtheria-pertussis-tetanus (DPT) vaccine (the first dose) or a measles vaccine between April 1, 1995 and December 31, 1997 in Takamatsu City to children with convulsions. DPT and measles vaccines were administered to 300 and 339 such(More)