Theoretical investigation of the lattice dynamics of GaAlSb superlattices

We investigate from first principles the effect of substitutional disorder on the off-resonance Raman activity of GaSb/AlSb superlattices (SLs) including strain and mixing effects. The method we use is based on a perturbation scheme which allows to take into account both the actual chemical configuration and local displacements from a given reference (virtual) system. We calculate the first-order Raman spectra of different (GaSb)n(AlSb)n superlattices grown in the [0 0 1] direction. The investigation of the effects of the interface modes on the Raman spectra allows the correct interpretation of the features found in the experiment.