KINETICALLY CONTROLLED CRITICAL THICKNESS FOR COHERENT ISLANDING AND THICK HIGHLY STRAINED PSEUDOMORPHIC FILMS OF INXGA1-XAS ON GAAS(100)

We have investigated the effects of surface-diffusion kinetics on the molecular-beam-epitaxy growth of highly strained InxGa1-xAs on GaAs(100). Experiments consisted of growing films at different substrate temperatures and characterizing them using reflection high-energy electron diffraction, scanning tunneling microscopy, and transmission electron microscopy. From a theoretical analysis we have obtained a criterion for a kinetically controlled critical thickness for coherent island formation that is in qualitative agreement with our experimental observations. The results of our study lead us to conclude that surface diffusion is a major factor determining the growth mode in strained-layer heteroepitaxy. As an example, it is shown that with limited kinetics (in this case, low temperatures) thick highly strained pseudomorphic layers may be grown.