The nonlinear effects in 2DEG conductivity investigation by an acoustic method

TL;DR

This study investigates nonlinear effects in 2DEG conductivity using an acoustic method, focusing on electron heating and energy relaxation in GaAs/AlGaAs heterostructures under magnetic fields.

Contribution

It introduces a contactless acoustic approach to analyze nonlinear 2DEG conductivity and characterizes electron heating and energy relaxation times.

Findings

Nonlinear SAW absorption is linked to electron heating in 2DEG.

Electron energy relaxation time is influenced by scattering at piezoelectric phonons.

Heating mechanisms depend on the relation between frequency and relaxation time.

Abstract

The parameters of two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure were determined by an acoustical (contactless) method in the delocalized electrons region ($B\le$2.5T). Nonlinear effects in Surface Acoustic Wave (SAW) absorption by 2DEG are determined by the electron heating in the electric field of SAW, which may be described in terms of electron temperature $T_e$. The energy relaxation time $\tau_{\epsilon}$ is determined by the scattering at piezoelectric potential of acoustic phonons with strong screening. At different SAW frequencies the heating depends on the relationship between $\omega\tau_{\epsilon}$ and 1 and is determined either by the instantaneously changing wave field ($\omega\tau_{\epsilon}$$<1$), or by the average wave power ($\omega\tau_{\epsilon}$$>1$).