SURFACE EVOLUTION DURING MOLECULAR-BEAM EPITAXY DEPOSITION OF GAAS

Scanning tunneling microscopy studies have been performed on GaAs homoepitaxial films grown by molecular-beam epitaxy. Images show that in the earliest stages of deposition the morphology oscillates between one with two-dimensional islands and flat terraces. As growth proceeds there is a gradual coarsening of the surface features. Comparison with reflection high-energy electron diffraction (RHEED) leads us to propose that there is a direct correspondence between the surface step density and the RHEED specular intensity. As such, we associate the decay of the RHEED oscillation amplitude with a reduction in the temporal variation of the step density rather than the buildup of interface width.