Composition of self-assembled Ge/Si islands in single and multiple layers

The degree of Si alloying in vertically aligned self-assembled Ge islands increases with the number of stacked layers. We find that the Si-Ge interdiffusion coefficient increases by more than two orders of magnitude for stacked hut clusters. Furthermore, we determine the composition profiles through the center of dome-shaped islands, capped with Si. These profiles exhibit a plateau near the base and a Ge enrichment near the apex of the islands. In this case, too, the upper dome island experiences a state of increased alloying with Si. (C) 2002 American Institute of Physics