Surface and interface ordering on non-(100)-oriented GaAs substrates

Abstract

We have observed the formation of highly ordered surface structures on (211), (311), and (111) GaAs substrates. During molecular-beam epitaxy, the flat surfaces break up into regular facets that have nanometer-scale dimensions, which can be directly monitored by reflection high-energy electron diffraction (RHEED). The RHEED intensity dynamics reveals a unique growth mechanism on the stepped surfaces during the growth of GaAs/AlAs multilayer structures resulting in the formation of alternating narrow and wide regions of GaAs and AlAs. The observed energy shift of the luminescence is correlated with the height of the specific surface corrugation and with the average GaAs layer thickness. The additional lateral confinement introduced by the interface corrugation manifests itself in an increased exciton continuum energy, an enhanced exciton-phonon interaction, a pronounced optical anisotropy, and an increased integral luminescence intensity. The observed surface structures offer a unified picture to explain previously unclear results obtained from these non-(100)-oriented GaAs surfaces, and they provide a unique method to directly synthesize quantum-wire and quantum-dot structures.