The investigation of the high frequency hopping conductivity in two- and three-dimensional electron gas by an acoustic method

High-frequency (HF) conductivity ($\sigma_{hf}$) measured by an acoustical method has been studied in GaAs/AlGaAs heterostructures in a linear and nonlinear regime on acoustic power. It has been shown that in the quantum Hall regime at magnetic fields corresponding to the middle of the Hall plateaus the HF conductivity is determined by the sum of the conductivity of 2-dimensional electrons in the high-mobility channel and the hopping conductivity of the electrons in the doped thick AlGaAs layer. The dependence of these conductivities on a temperature is analyzed. The width of the Landau level broadened by the impurity random potential is determined.