1. Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Lavrent'ev ave., 13, Novosibirsk 630090, Russia
2. Novosibirsk State University, Pirogova street, 2, Novosibirsk 630090, Russia
3. Novosibirsk State Technical University, K. Marx ave., 20, Novosibirsk 630073, Russia
4. National Chiao Tung University, Hsinchu 300, Taiwan
5. Université de Lorraine, CNRS, IJL, F-54000 Nancy, France