NEW MODEL FOR REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION INTENSITY OSCILLATIONS

We investigate the influence of inelastic processes on reflection high -energy electron diffraction (RHEED) oscillations by recording energy filtered RHEED intensity oscillations during homoepitaxy of (001)-orie nted GaAs. The results clearly show that the dominant inelastic scatte ring process, plasmon inelastic scattering, does not influence the pha se of the oscillations. It cannot therefore account for an independent process contributing a phase to the oscillations that is different fr om elastic scattering. As an alternative approach, we investigate a ba sic coherent scattering model introduced by Horio and Ichimiya. We com pare its predictions with experiments in the one-beam condition for bo th GaAs and AlAs(001) homoepitaxy. The average crystal potential requi red for the fits can be determined independently by Kikuchi line fits, yielding a value of 10.5 +/- 0.5 V for both GaAs and AlAs. This allow s us to reduce the number of free parameters in the model to only the layer thickness. The theoretical fits of the model to the experimental data yield different layer thicknesses that are in good agreement wit h the surface reconstruction thicknesses for GaAs and AlAs. We therefo re conclude that the phase of RHEED oscillations is determined by the surface reconstruction forming on top of the growing layer during crys tal growth. This new model explains many experimentally observed RHEED oscillation phenomena in a unified approach. (C) 1998 American Vacuum Society.