1. Institute of Physics; AS CR; Na Slovance 2 18221 Prague 8 Czech Republic
2. V.E. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine; pt.Nauky 41 03028 Kiev Ukraine
3. Leipzig University; Linnéstrasse 5; 04103 Leipzig Germany
4. St. Petersburg State University; Ulianovskaya 1; 198504 St. Petersburg Russia
5. A.F. Ioffe Physical Technical Institute; RAS; Polytechnicheskaya 26 194021 St. Petersburg Russia