Compositional evolution of SiGe islands on patterned Si (001) substrates

The authors investigate, by atomic-force-microscopy-based nanotomography, the composition evolution of ordered SiGe islands grown on pit-patterned Si (001) substrates as their size and aspect ratio increase with increasing Ge deposition. Compared to islands grown on flat substrates, the ordered island arrays show improved size, shape, and compositional homogeneity. The three-dimensional composition profiles of individual pyramids, domes, and barns reveal that the Ge fraction at the base and in subsurface regions of the islands decreases with increasing amount of deposited Ge.