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.