Quantitative comparison of surface morphology and reflection high-energy electron diffraction intensity for epitaxial growth on GaAs

The relationship between developing surface morphology and specular spot intensity in reflection high-energy diffraction (RHEED) has been investigated during the homoepitaxial growth of GaAs on various surface orientations. The ‘morphological’ quantities of step density and effective coverage have been measured directly by means of rapid-quench scanning tunnelling microscopy (STM). For growth on the singular (001), (110) and (111)A surfaces, the step density, layer coverage and RHEED intensity oscillate with a period of one monolayer and little damping. The morphological quantities are always in phase, while the phase of the RHEED intensity depends on the diffraction conditions. On vicinal GaAs(001), the RHEED intensity oscillations are rapidly damped, as are oscillations of the morphological quantities, but again the phase of the RHEED intensity can be varied with respect to the other two. In all cases on the (001) surface, a well-ordered (2×4) surface reconstruction develops very rapidly in the growing layer. Implications for theories of RHEED intensity oscillations are discussed.