Affiliation: | (1) Semiconductor Research Institute, Aoba 519–1176, Aramaki, Aoba-ku, Sendai 980–0845, Japan;(2) Terahertz laboratory, Co.Ltd, Maedamen 50–1, Mitsumata, Komagata-cho, Yuzawa, Akita 012–0104, Japan;(3) Department of Material Science, Tohoku University, Aoba-yama 6–6–11–1021, Sendai 980–8579, Japan |