Morphology of strained and relaxed SiGe layers grown on high-index Si substrates

We have investigated the surface morphology of strained and relaxed SiGe layers grown on Si substrates with surface normals rotated off of the [001] axis towards [111] by 0, 13, and 25°. Atomic force microscopy has revealed surface corrugations in thin layers prior to plastic relaxation on each of the surfaces due to the initial deposition of the strained films. Thicker partially relaxed layers have previously been shown to contain networks of misfit dislocations which create patterns that are unique to each substrate orientation. We find on these relaxed layers that the surface corrugations are well aligned with the dislocation networks forming a modified crosshatch pattern on the off-axis substrates. More strikingly, though, we find that these corrugations are comprised of smaller nanostructured features which are also unique to each surface. Topographs of the unrelaxed surfaces show no such organization indicating a correspondence between the misfit dislocations and the surface corrugations.