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≤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 Te. The energy relaxation time τϵ 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 ωτϵ and 1 and is determined either by the
instantaneously changing wave field (ωτϵ<1), or by the
average wave power (ωτϵ>1).Comment: RevTeX, 5 pages, 3 PS-figures, submitted to Physica Status
Sol.(Technical corrections in PS-figs