Elimination of dislocations in bulk GaAs crystals grown by liquid-phase electroepitaxy

Abstract

The dislocation density in bulk GaAs crystals (up to 4 mm thick) grown by liquid-phase electroepitaxy (LPEE) is found to be significantly reduced (by as much as a factor of 20) relative to that in the substrate. This reduction takes place when the thickness of the growing crystal exceeds a critical value of 50–70 μm. It is accompanied by a formation of misfit dislocation arrays identified by transmission electron microscopy in the interface region between the substrate and grown crystals. These findings suggest that the reduction of the dislocation density is caused by a small but finite lattice mismatch between the growing epitaxial-quality crystal and the relatively inferior quality melt-grown substrate. Dislocations which propagate from the substrate into the LPEE crystal are forced by the misfit stress to move laterally forming misfit dislocations.