Electron localization in sound absorption oscillations in the quantum Hall effect regime

The absorption coefficient for surface acoustic waves in a piezoelectric insulator in contact with a GaAS/Al(0.25)Ga(0.75)AS heterostructure (with two-dimensional electron mobility mu = 1.3 x 10(5) cm(2)/(V.s) at T = 4.2 K) via a small gap has been investigated experimentally as a function of the frequency of the wave, the width of the vacuum gap, the magnetic field, and the temperature. The magnetic field and frequency dependences of the high-frequency conductivity (in the region 30-210 MHz) are calculated and analyzed. The experimental results can be explained if it assumed that there exists a fluctuation potential in which current carrier localization occurs. The absorption of the surface acoustic waves in an interaction with two-dimensional electrons localized in the energy ''tails'' of Landau levels is discussed. (C) 1997 American Institute of Physics.