Surface effects and growth dynamics in MBE of III–V compounds

Abstract

The forward scattering geometry of reflection high-energy electron diffraction (RHEED) makes it particularly suitable for in-situ studies of the growth dynamics involved in molecular beam epitaxy (MBE). Diffracted intensities can be measured continuously and their periodic variation enables growth processes to be monitored with atomic layer precision. Analysis using a single scattering diffraction theory leads to a simple layer-by-layer two-dimensional growth model, but the limitations which are imposed by the experimentally demonstrated multiple-scattering nature of the diffraction process are discussed with particular reference to reconstructed GaAs(001) surfaces. Multiple-scattering effects can be used to advantage however, to resolve the phase and waveform behaviour of the oscillations by measurement over a wide range of diffraction conditions. A more detailed growth model has been developed from these results. Reported improvements (smoothing) in the quality of heterointerfaces in quantum wells and superlattices resulting from interrupted growth cannot be related simply to the changes in diffracted intensity which occur when growth is terminated, contrary to previous suggestions in the literature.