Energy losses of 2D electron gas due to near-surface acoustic phonon scattering

We have shown that for quantum wells placed close to the stress-free surfac e of the semiconductor heterostructure, the energy relaxation rate of two-d imensional electrons interacting with acoustic phonons at low temperatures (Bloch-Gruneisen regime) is changed considerably in comparison with that of a two-dimensional electron gas placed in a bulk of semiconductor. The rela xation rate is enhanced in the case of a semiconductor-vacuum system and is suppressed in the case of the surface covered by a thin metal him. The enh anced energy loss is caused by additional scattering at localized and refle cted acoustic waves, and the decrease appears due to suppression of piezoel ectric scattering in the vicinity of the metal. (C) 2000 Academic Press.