1. Kremenchuk State Polytechnical University, 20 Pershotravneva St., 39614 Kremenchuk, Ukraine
2. Institute of Semiconductor Physics, SB RAS, 13 Lavrentieva Av., 630090 Novosibirsk, Russia
3. R & D Institute for Materials SRC “Carat”, 202 Stryjska St., 79031 Lviv, Ukraine
4. Institute of Semiconductor Physics, NASU, 45 Nauki Av., 03028 Kiev, Ukraine