1. Advanced Technology R&D Center, Mitsubishi Electric Corporation, 8-1-1 Tukaguchi-Honmachi, Amagasaki, Hyogo 661-8661, Japan
2. Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
3. Power Device Works, Mitsubishi Electric Corporation, 1-1-1 Imajuku-Higashi, Nishi-ku, Fukuoka, Fukuoka 819-0192, Japan