A study was made of the growth topology and defect structure of hetero-epitaxial Si0.8Ge0.2 layers which had been grown, by means of ion-beam sputter deposition (20keV Xe+), onto (001) Si substrates. Transmission electron microscopy and atomic force microscopy showed that the sputtered surfaces, at all growth temperatures, were quite smooth; with a mean surface roughness of less than 1.8nm. It was noted that there was a tendency for the quality to improve with increasing growth temperature. This was attributed to the longer diffusion length of adatoms at the SiGe layer surface. The lattice defects which were observed in the SiGe layer could be classified into misfit-induced defects such as dislocations, and defects (parallel to {113} and {001} lattice planes) which existed due to bombardment of the growing film with high-energy Si and Ge atoms. The {113} defects were explained in terms of the agglomeration of a supersaturation of point defects. At a growth temperature of 700C, an enhanced diffusion of point defects to the layer surface and to the Si substrate reduced the supersaturation, and the nucleation of {113} and {001} defects was thereby suppressed.

V.Demuth, W.Dorsch, H.P.Strunk, M.Lyakas, M.Eizenberg, N.Mosleh, F.Meyer, C.Schwebel: Solid State Phenomena, 1996, 47-48, 431-6