Anisotropy of optical phonons and interface modes in GaAs-AlAs superlattices

Abstract
In this paper phonon properties of GaAs-AlAs superlattices are studied with an 11-parameter rigid-ion model. Short-range interactions up to the second neighbors are included, and the long-range Coulomb interaction is calculated exactly. Modes propagating both normally (k?=0) and obliquely (k?≠0) to the interfaces are studied for a number of GaAs-AlAs superlattices. Anisotropy of zone-center optical phonons is examined in detail. Phonon dispersion relations of large-size GaAs-AlAs superlattices are calculated and many interface modes are identified. All results are compared with the existing experimental data with favorable agreement.