1. Rzhanov Institute of Semiconductor Physics (SB RAS), 13 Lavrentiev Av., Novosibirsk 630090, Russia
2. Semiconductor Physics and Center for Materials, Architectures and Integration of Nanomembranes (MAIN), Chemnitz University of Technology, D-09107 Chemnitz, Germany
3. Novosibirsk State University, 1 Pirogova Str., Novosibirsk 630090, Russia