Temperature dependence of the Raman spectrum ofAlxGa1−xAsternary alloys

Abstract

We have studied the effect of the temperature on the first-order Raman spectra of ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ alloys. The temperature induced frequency shift is studied over the full composition range between 300 and 650 K. It is found that the frequency temperature coefficient, $d\ensuremath{\omega}/dT,$ is higher for AlAs-like modes than for GaAs-like modes and it increases with x. Linewidth and frequency shift data were analyzed in terms of anharmonicity, thermal expansion, and cation dilution. Anharmonicity was found to be the dominant term in the variation of the temperature dependence of the frequency of AlAs modes for different alloy compositions, while thermal expansion has a high influence on GaAs modes. The linewidth data are interpreted in terms of the contribution to the Raman spectrum of phonons with $\mathbf{q}\ensuremath{\ne}0$ and cation dilution.