Surface structure and the origin of antisite domains in GaAs:Ge epitaxial films

Abstract

The growth of epitaxial films of GaAs on Ge substrates is considered. It has been shown in a previous paper that antisite domains can arise in the GaAs layer when the substrate orientation is { hk0}. Such antisite domain boundaries separate energetically degenerate interfacial domains which are related by symmetry operations. In the present work the origin of antisite domains in { hk0} specimens is investigated from the point of view of complementary surface structures on the substrate and overlayer. It is shown that the origin of antisite disorder is different depending on whether h and k, which are integers having no common factor, are mixed (i.e. one odd and one even) or are both odd. In the former case antisite disorder is shown to arise as a consequence of the existence of a previously unrecognised type of step which can exist on the Ge substrate. In the latter case the disorder is shown to be a consequence of the lower symmetry of a GaAs surface compared with that of the complementary Ge surface.