1. A.V. Rzhanov Institute of Semiconductor Physics, pr. Lavrentieva 13, 630090 Novosibirsk, Russia
2. Novosibirsk State University, Pirogov str. 2, 630090 Novosibirsk, Russia
3. Department of Chemistry, Moscow State University, 119991 Moscow, Russia
4. Department of Material Science, Moscow State University, 119991 Moscow, Russia
5. Institute of Automation and Electrometry, Ac. Koptyuga ave., 1, 630090 Novosibirsk, Russia
6. Semiconductor Physics, Chemnitz University of Technology, D-09107 Chemnitz, Germany