1. Frontier Research Academy for Young Researchers, Kyushu Institute of Technology, 680-4 Kawazu, Iizuka, Fukuoka 820-8502, Japan
2. Department of Electronic Devices Engineering, Graduate School of Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611, Japan
3. National College of Technology, Ube College, 2-14-1 Tokiwadai, Ube 755-8555, Japan