Investigations were made of near-surface diffusion during the formation of self-assembled Ge islands on Si(001). The detailed shapes of trenches around islands, that formed due to short-range strain-enhanced diffusion, were measured. It was found that the trenches had anisotropic shapes, and these were explained in terms of the intrinsic anisotropy of the elastic properties of the Si crystal. Long-range depletion of the substrate and trench formation between neighbouring islands, due to strong Si in-diffusion into nominally pure Ge islands, was observed at high growth temperatures. A simple diffusion model, which predicted trench depths as a function of island separation, fitted the experimentally observed data. The calculated diffusion lengths, according to this model, were comparable to the average island separation on the surface.

Trench Formation around and between Self-Assembled Ge Islands on Si. U.Denker, O.G.Schmidt, N.Y.Jin-Philipp, K.Eberl: Applied Physics Letters, 2001, 78[23], 3723-5