We review the rate equation method of modeling epitaxial growth on a flat surface, where the predominant growth mode is via nucleation and growth of adatom islands. We apply a similar method to investigate the step-edge propagation growth mode on stepped (vicinal) surfaces. Unlike the intuitive picture of step-edge propagation whereby the surface morphology is invariant in a moving reference frame, results show oscillations in the step-edge positions about mean values (dependent on initial step-edge distribution). This could have important consequences in the growth of vertical superlattices. We have combined the two previous models to describe a more general case of growth, on stepped surfaces, where both nucleation through adatom islands and step-edge growth occur. Calculated reflection high-energy electron diffraction oscillations from this model will be compared with experimental results.
The intensities of several reflection high-energy electron diffraction (RHEED) beams have been recorded during molecular-beam epitaxial growth of GaAs(100) using a novel video intensity measurement system that records multiple RHEED beam intensities simultaneously. The RHEED beam intensities were recorded at varying angles of incidence and crystal substrate azimuth angles. Strong oscillations in the intensities in specular and nonspecular beams with the same period but varying phases have been measured. As noted by other investigators, the phase relationship of the oscillations of the various beams has been found to vary with incident and azimuthal angle. The results are examined with regard to recent studies of the role of Kikuchi processes on the phase of the specular beam. In contrast to other reports, it is found that although the diffracted intensities in the vicinity of the elastically diffracted beams are influenced by inelastically scattered electrons from the Kikuchi lines, these effects can not account for all the phase behavior observed.
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