Dynamics of non-equilibrium short-wave-length phonons in semiconductor heterostructures

The behavior of short-wave-length acoustic phonons in the vicinity of a quantum well in a GaAs/AlGaAs heterostructure has been investigated. Hot two-dimensional electrons in the well produce longitudinal optical phonons, which decay into almost monoenergetic short-wave-length longitudinal acoustic (LA) phonons. The latter undergo elastic scattering and down-conversion into transverse acoustic (TA) phonons. The distribution of the LA and TA phonons over frequency and distance to the well have been found by solving semi-analytically a system of two kinetic equations with non-trivial boundary conditions and nonlinear dispersion. The distribution functions have essentially non-temperature form even at substantial distance from the well.