Picosecond Raman studies of the Frohlich interaction in semiconductor alloys

Abstract

Picosecond Raman studies on the prototypic alloys Al_xGa_1-xAs and In_xGa_1-xAs show that substantial nonequilibrium phonon effects occur in spite of the break-down in wave-vector conservation engendered by alloy disorder. Phonon lifetimes, measured to be the same as in pure GaAs, also are unaffected by the disorder. Explicit expressions for the Frohlich couplings of the two LO phonon modes in Al_xGa_1-xAs are obtained to compare with the generation rates of these phonons measured in our experiments.