The local Ge composition in undulating Si0.8Ge0.2layers on Si was studied by means of scanning transmission electron microscopy, using electron energy-loss spectroscopy. Enrichment in Ge of the SiGe layer, near to the free surface (vertical Ge segregation in the growth direction), was observed as well as Ge depletion of the ripple troughs as compared with the peaks (lateral segregation). Such lateral compositional fluctuations were expected to retard the generation of misfit dislocations, and to be relevant to the Stranski-Krastanov growth of strained epitaxial alloy layers or the self-organized growth of quantum-dot structures.

T.Walther, C.J.Humphreys, A.G.Cullis: Applied Physics Letters, 1997, 71[6], 809-11