Mechanisms of strain relaxation and defect formation, during the surface roughening of films which were grown epitaxially onto (100)Si substrates, were investigated by means of controlled annealing experiments. Epitaxial films which were 10nm in thickness and contained 18% Ge (sub-critical with respect to the formation of misfit dislocations) exhibited strain relaxation via surface roughening, during annealing at 850C. Surface grooves were aligned along (100) directions. In 22%Ge films with a super-critical thicknesses, the surface grooves were aligned along (110) directions.

C.S.Ozkan, W.D.Nix, H.Gao: Applied Physics Letters, 1997, 70[17], 2247-9