1. Vilnius University, Faculty of Physics, Sauletekio al. 9, Building III, LT-10222 Vilnius, Lithuania
2. Vilnius University, Faculty of Physics, Sauletekio al. 9, Building III, LT-10222 Vilnius, LithuaniabVilnius University, Institute of Applied Research, Sauletekio al. 9, Building III, LT-10222 Vilnius, Lithuania
3. Vilnius University, Faculty of Physics, Sauletekio al. 9, Building III, LT-10222 Vilnius, LithuaniacSemiconductor Physics Institute of the Center for Physical Sciences and Technology, A. Goštauto g. 11, LT-01108 Vilnius, Lithuania