1. A.V. Rzhanov Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090, Russia
2. Novosibirsk State University, Novosibirsk 630090, Russia
3. Université de Lorraine, Institut Jean Lamour UMR CNRS 7198, B.P. 70239, 54506 Vandœuvre-lès-Nancy Cedex, France