1. Institute for Physics of Microstructures of Russian Academy of Sciences, 603950 Nizhny Novgorod, Russia
2. Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod, Russia
3. UMR CNRS 5221, GIS-TERALAB, Université Montpellier II, 34095 Montpellier, France
4. A.V. Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia
5. Novosibirsk State University, 630090 Novosibirsk, Russia