3:45 PM - 4:00 PM △ [20p-E311-9] Electrical Properties of High-Purity Semi-Insulating 4H-SiC Substrates Annealed at High Temperature or Thermally Oxidized 〇Chansoon Koo1, Mitsuaki Kaneko1, Tsunenobu Kimoto1 (1.Kyoto Univ.)