1. Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, prospekt Lavrent’eva 13, 630090 Novosibirsk, Russia
2. Department of Physics, Novosibirsk State University, 630090 Novosibirsk, Russia
3. Scientific-Practical Material Research Centre of the National Academy of Science of Belarus, P. Brovki 19, 220072 Minsk, Belarus