1. Lappeenranta University of Technology, Laboratory of Physics, School of Engineering Science, Lappeenranta, Finland
2. Lappeenranta University of Technology, Laboratory of Physics, School of Engineering Science, Lappeenranta, FinlandbIoffe Physical Technical Institute, Laboratory of Nonequilibrium Processes in Semiconductors, Division of Solid State Electronics, St. Petersburg, Russia
3. South Ural State University, Education and Research Center for Nanotechnology, Chelyabinsk, Russia