[1] Natl Res Ctr Kurchatov Inst, Moscow 123182, Russia
[2] Lomonosov Moscow State Univ, Fac Phys, Moscow 119991, Russia
[3] Voronezh State Tech Univ, Fac Radio Engn & Elect, Dept Solid State Phys, Voronezh 394026, Russia
[4] State Univ, Moscow Inst Phys & Technol, Dolgoprudnyi 141700, Russia
[5] RAS, Kotelnikov Inst Radio Engn & Elect, Fryazino 141190, Russia