1. Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentiev Ave., 630090 Novosibirsk, Russia
2. Novosibirsk State University, 2 Pirogov Str., 630090 Novosibirsk, Russia
3. Novosibirsk State Technical University, 20 Marx ave., 630073 Novosibirsk, Russia
4. Department of Electronics Engineering, National Chiao Tung University, Hsinchu 300, Taiwan