2ND-ORDER RAMAN-SPECTROSCOPY OF ALAS - A TEST OF LATTICE-DYNAMICAL MODELS

The second-order Raman spectrum of AlAs has been measured on samples g rown by molecular-beam epitaxy (MBE). The results show significant dis crepancies with model calculations of the phonon density of states, bu t are consistent with recent first-principles calculations. This first -principles approach has been used to compute the phonon energies in G aAs-AlAs superlattices, with controversial implications regarding the sharpness of MBE-grown interfaces. The Raman results presented here su pport the conclusions of the first-principles analysis.