AlAs-like TO-phonon dephasing time in high Al content AlGaAs

Abstract

The AlAs-like TO-phonon decay in Al0.7Ga0.3As has been investigated using an infrared four wave mixing technique with picosecond resolution. The low temperature TO-phonon lifetime is found to be ~5 ps and is significantly shorter than ~40 ps recently predicted for the TO-phonon in AlAs [A. Debernardi, Phys. Rev. B 57, 12847 (1998)]. In alloy materials Al and Ga atoms are randomly distributed on the Group III sublattice of the zincblende structure. This disorder considerably reduces the lifetime of AlAs phonon mode due to scattering of the TO phonon with Ga atoms which results in an additional decay channel: AlAs-TO→ GaAs-L(T)O+LA in AlGaAs alloy materials. The new decay channel also leads to stronger temperature dependence of the TO-phonon lifetime. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.