Lattice dynamics of GaAs/AlAs superlattices

Abstract We report on the results of three-dimensional shell model calculations of GaAs/AlAs super- lattice phonon frequencies and eigenvectors. Their dependence on direction and magnitude of the wavevector is investigated. Among others we find the occurrence of acoustical (Lamb- and Love-like) guided and optical (Fuchs-Kliewer-like) interface phonons for wavevectors perpendicular to the layer normal; for wavevectors parallel to the normal there are folded and confined phonons. For the folded phonons the ionic displacements can be described by continuously matched sine and cosine functions. An effective wavevector can be attributed to the confined phonons. With this wavevector Raman data in superlattices are reevaluated and compared with recent high-accuracy neutron scattering data for bulk GaAs.