Reflection high-energy electron diffraction intensity oscillations during Si growth on Ge(001) by solid source molecular beam epitaxy

RHEED intensity oscillations of the specular beam are used to follow the growth of Si on Ge(001) by solid source molecular beam epitaxy (SSMBE) in a large range of substrate temperatures and Si deposition rates. From room temperature to 300 degrees C, a kinetic governed layer-by-layer growth mode is observed, the periods of the oscillations corresponding to a single atomic layer. The slow damping of the oscillations in this regime is related to a progressive appearance of surface defects, the RHEED patterns remaining two-dimensional but becoming more diffuse after complete damping of the oscillations. The damping is faster at either higher temperature or lower deposition rates, both effects favouring the increase of the surface diffusion length. Thus, at 400 degrees C, only two oscillations with a doubled period are observed before damping. At 500 degrees C, no RHEED oscillations are obtained in line with the setting up of the thermodynamically expected Volmer-Weber growth mode. (C) 1998 Elsevier Science B.V. All rights reserved.