1. Semiconductor Physics, Chemnitz University of Technology, Chemnitz, Germany
2. A.V. Rzhanov Institute of Semiconductor Physics, Novosibirsk, Russia
3. Novosibirsk State University, Novosibirsk, Russia
4. Department of Chemistry, Moscow State University, Moscow, Russia
5. Department of Material Science, Moscow State University, Moscow, Russia
6. V.E. Lashkaryov Institute of Semiconductor Physics, UA-03028 Kiev, Ukraine