A detailed study was made, of hetero-epitaxial InxGa1-xAs layers on GaAs, by means of

transmission electron microscopy and atomic force microscopy. The characteristics of the low x-value smooth-growth regime were explained in terms of surface step configurations. A progressive increase in the irregularities of step fronts, and monolayer island formation with increasing In content, were correlated with a transition to undulating growth which occurred as an x-value of 0.25 was approached. The evolution of high x-value roughened layers was studied, and structural changes with increasing film thickness and In content were determined. The manner in which fine ripple arrays evolved from isolated islands, and the stress interaction between islands, was investigated. The magnitude of the periodic elastic stress field which accompanied the formation of ripple structures was measured and was shown to yield essentially complete misfit relief within the ripple crests. The increased stresses which were present at ripple troughs were shown to lead to a misfit defect source behavior which was expected to be of importance with respect to defect generation in all strained undulating epitaxial films.

A.G.Cullis, A.J.Pidduck, M.T.Emeny: Journal of Crystal Growth, 1996, 158[1-2], 15-27