THE INVESTIGATION OF THE HIGH-FREQUENCY HOPPING CONDUCTIVITY IN 2-DIMENSIONAL AND 3-DIMENSIONAL ELECTRON-GAS BY AN ACOUSTIC METHOD

High-frequency (HF) conductivity (sigma(hf)) measured by an acoustical method las been studied in GaAs/AlGaAs heterostructures in a linear a nd nonlinear regime on acoustic power. It has been shown that in the q uantum Hall regime at magnetic fields corresponding to the middle of t he Hall plateaus the HF conductivity is determined by the sum of the c onductivity of two-dimensional electrons in the high-mobility channel and the hopping conductivity of the electrons in the doped thick AlGaA s layer. The dependence of these conductivities on temperature is anal yzed. The width of the Landau level broadened by the impurity random p otential is determined.