Morphology of GaAs crystals heterogeneously integrated on nominal (001) Si by epitaxial lateral overgrowth on tunnel oxide via Ge nano-seeding

In this study, GaAs crystals were grown by chemical beam epitaxy on nominal (001) Si substrate over Ge nano-seeds placed within nano-holes opened through a 0.6 nm silica layer. GaAs crystal morphology and atomic organization at the interface between Ge and GaAs were studied by using complementary Scanning Transmission Electron Microscopy, energy dispersive X-ray spectrometry and dark-field electron holography. Fourfold symmetry GaAs crystals were obtained and found to be completely relaxed and twin free. Thus, the use of Ge nano-seeds to initiate the growth of GaAs results in the suppression of twins previously observed for direct GaAs growth on nominal (001) Si. Nevertheless, anti-phase domains were detected. A simple atomistic model is proposed which explains how Anti-Phase Boundaries develop at the junctions between Ge {113} facets, and {113} and {111} facets for As-stabilized GaAs growth.