Angular and mode distribution of acoustic phonon emission by hot 2D electrons in GaAs: the effect of acoustic anisotropy and screening

We report a detailed theoretical study of the angular and polarization depe ndence of the acoustic phonon emission by a hot two-dimensional electron ga s (2DEG) in GaAs/AlGaAs heterojunctions and quantum wells (QW) and compare the results with some recent heat pulse measurements. We use a model which nor only includes the dynamical screening of electron-phonon interaction bu r also takes proper account of the finite "thickness" of the 2D gas and abo ve all, considers the strong acoustic anisotropy of the electron-phonon mat rix elements and the propagation process. For QW with different widths we d emonstrate the strong dependence of the angular distribution on the well wi dth. For heterostructures in the (001)-plane,we can explain, in contrast to earlier theoretical studies, the phenomena of missing longitudinal modes f or phonon emission close to the two-dimenional electron gas (2DEG) normal. (C) 1999 Elsevier Science B.V. All rights reserved.