LATTICE-DYNAMICS AND RAMAN RESPONSE OF (113) GAAS ALAS SUPERLATTICES/

We present a supercell model calculation of the vibrational properties and Raman response of (113)-oriented GaAs/AlAs superlattices. Phonon- dispersion relations are calculated both along the growth axis and in the normal planes. The angular dispersion of the zone-center optical p honons is calculated as well, and some unusual features are discussed. We also calculate the Raman response in the backscattering geometry: to this aim, the bond polarizability model has been suitably extended to the case of arbitrarily oriented superlattices. The effects of the interface cationic diffusion on the Raman spectra are discussed. A com parison with experimental data is finally presented and discussed.