A.A. Teplykh - Ph. D. (Phys.-Math.), Senior Research Scientist, Laboratory of Physical Acoustics, Saratov branch of Kotel\'nikov IRE of RAS. E-mail: teplykhaa@mail.ru B.D. Zaitsev - Dr. Sc. (Phys.-Math.), Professor, Head of Laboratory of Physical Acoustics, Saratov branch of Kotel\'nikov IRE of RAS. E-mail: zai-boris@yandex.ru I.E. Kuznetsova - Dr. Sc. (Phys.-Math.), Associate Professor, Leading Research Scientist, Laboratory of Electronic Processes in Semiconductor Devices, Kotel\'nikov IRE of RAS (Moscow). E-mail: kuziren@yandex.ru