SURFACE EVOLUTION IN GAAS(110) HOMOEPITAXY - FROM MICROSCOPIC TO MACROSCOPIC MORPHOLOGY

The surface evolution of GaAs(1 1 0) thin films grown under different conditions by molecular beam epitaxy has been studied by reflection hi gh-energy electron diffraction, in situ scanning tunnelling microscopy and ex situ Nomarski interference optical microscopy. For various con ditions of substrate temperature and As/Ga flux ratio, STM and Nomarsk i microscope images of 0.5 and 1000 ML depositions have been correlate d with different growth regimes identified by RHEED intensity oscillat ion studies. The surfaces exhibit very different morphologies specific to the growth regime studied. For the more important growth modes (mo nolayer-by-monolayer, bilayer-by-bilayer and step decoration), STM has also been used to follow the evolution of the surface in the early st ages of homoepitaxy (0-2 ML). The results indicate that the smoothest films are grown under As-rich conditions and at low substrate temperat ures, and this correlates with a step decoration growth mode. (C) 1998 Elsevier Science B.V. All rights reserved.