TRANSMISSION ELECTRON-MICROSCOPY CHARACTERIZATION OF INXGA1-XAS SUBSTRATES GROWN BY HETEROEPITAXIAL LATERAL OVERGROWTH

InxGa1-xAs (x = 0.04) ingots have been grown by liquid phase electroep itaxy (LPEE) on GaAs (001) substrates covered with a 0.2 mum thick SiO 2 layer using a heteroepitaxial lateral overgrowth technique. Growth b egins in 10 mum wide oxide-free seeding windows oriented at approximat ely 30-degrees to the {110} planes of the substrate, and proceeds late rally over adjacent 90 mum wide oxide strips. Transmission electron mi croscopy (TEM) analysis of the resulting material reveals a decrease i n dislocation densities in the alloy layer, as dislocation nucleation occurs only at the seeding windows, while growth proceeds defect-free over the oxide. Etching the seeding windows slightly into the substrat e results in an increase in dislocation propagation into the substrate and under the oxide layer, and a lower dislocation density in the ove rlayer. The combination of the lateral overgrowth technique and the de eper window etching results in a significantly lower defect density in the InxGa1-xAs overlayer.