Optical phonons inAlxGa1−xAs: Raman spectroscopy

A detailed investigation was made using Raman spectroscopy of the longitudinal and transverse optical phonons in the disordered alloy ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ at room temperature. Spectra obtained for a large number of $x$ values were peak fitted to yield the optical phonon band parameters as a function of $x$. New expressions are obtained for the frequency variation with Al composition for the GaAs-like and AlAs-like modes, as well as the variations in linewidth, line asymmetry, and intensity for the two longitudinal modes. The results when compared with theoretical predictions indicate a need for further theoretical study.