1. Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentiev aven., Novosibirsk 630090, Russia
2. Novosibirsk State Technical University, 20 K. Marx str., Novosibirsk 630073, Russia
3. Joint Institute for High Temperatures RAS, 13 Izhorskaya str., Bld.2, Moscow 125412, Russia