Defects in molecular beam epitaxial films on GaAs(100), Ge(100) or Si(100) substrates were studied by using transmission electron microscopy and X-ray pole figures. It was found that growth twins, located preferentially on 2 of the 4 possible {111} planes, were the main defects. A mechanism for spontaneous twin formation was proposed on the basis of the orientation of the nuclei for 3-dimensional island nucleation and growth. The anisotropic distribution of twins and their visibility in cross-sectional transmission electron microscopy could be explained by using this model.

S.B.Sant, G.C.Weatherly, R.W.Smith: Philosophical Magazine A, 1999, 79[3], 561-75