NONEQUILIBRIUM PHONONS AND DISORDER IN Al//xGa//1// minus //xAs.

Abstract

Despite alloy disorder, picosecond Raman measurements show significant nonequilibrium phonon effects in Al//xGa//1// minus //xAs. The virtual crystal approximation is shown to apply. Implications for heterojunction devices are considered. Calculation of the Froelich matrix elements for the GaAs-like and AlAs-like models, shows that the coupling for the AlAs-like mode is small for small x. Furthermore, if the concept of the correlation length is carefully introduced properly, one can account for both the observed broadening in cw Raman scattering and the substantial hot phonon effects observed in the transient measurements reported.