SECOND-ORDER RAMAN-SPECTRA AND LATTICE-DYNAMICS IN ALAS

We have re-examined the second-order Raman spectra in a thick AlAs layer grown on a GaAs substrate by polarized Raman spectroscopy. So as to reproduce the spectra, the force constants have been refined and then the phonon dispersion has been calculated within a modified version of the adiabatic bond-charge model. We present phonon frequencies at critical points, e.g. Gamma, X, L and W, and the force constants for AlAs. The phonon dispersion is compared with a previous ab initio result and it is shown that the procedure presented herein is useful. A brief discussion is also given of the analysis of the second-order Raman spectra of AlSb