Resonant Raman scattering in [111] GaAs/AlAs short-period superlattices

Abstract

Resonant Raman scattering has been used to study short-period GaAs/AlAs superlattices grown along the [111] direction. Samples with moderately large periods (wells and barriers greater than 9 monolayers) show a direct band gap, while for a (6,6) monolayer sample the lowest-energy transition appears to be indirect in k space (but direct in real space), occurring between the GaAs \ensuremath{\Gamma} and L states. Confined optical phonons are clearly observed in resonant conditions, both for GaAs and AlAs; they yield information about the bulk optical-phonon dispersions of these materials along the \ensuremath{\Gamma}-L direction.