Compositionally graded strain-relaxed Si0.72Ge0.28 buffers were grown onto vicinal Si(001) substrates by means of gas-source molecular beam epitaxy. Misfit dislocations were shown to run along the intersections of the {111} glide planes and (11n) interface. The use of X-ray diffraction demonstrated a relative tilt of the epilayer with respect to the substrate, in a direction which depended upon the interplay between substrate orientation-related preferential dislocation nucleation rates and surface contamination-induced heterogeneous nucleation. Atomic force microscopic images revealed an anisotropy, in surface roughness at the micron scale, which was related to reduced growth rates on vicinal surfaces. The transport properties at 0.4K, in 2-dimensional electron gases grown onto these relaxed SiGe buffers, revealed anisotropic scattering times that were similar to an interface roughness scattering which could be correlated to terrace configurations in the nm-range, as determined by using atomic force microscopy.

P.Waltereit, J.M.Fernández, S.Kaya, T.J.Thornton: Applied Physics Letters, 1998, 72[18], 2262-4