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

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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 Γ 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 Γ-L direction.