Epitaxial lateral overgrowth of m-plane α-Ga2O3 by halide vapor phase epitaxy

Abstract

We demonstrated the epitaxial lateral overgrowth of m-plane α-Ga2O3 using halide vapor phase epitaxy. An m-plane α-Ga2O3/sapphire template with a patterned SiO2 mask was used as the substrate. The highest lateral growth rate for a radial spoke-wheel patterned mask was obtained when the spoke was perpendicular to the (Formula presented.) direction. In this case, the lateral-to-vertical growth rate ratio (L/V ratio), with L defined as the rate of increase in the width of an elongated α-Ga2O3 island, was as large as 5.8. This ratio was greater than that reported for an m-direction stripe mask on a-plane α-Ga2O3 by a factor of 3.3 and that for an a-direction stripe mask on c- and m-plane α-Ga2O3 by a factor of 13. The epitaxial lateral overgrowth (ELO) of α-Ga2O3 on a stripe mask (window/mask widths of 2.5 μm/7.5 μm) perpendicular to (Formula presented.) resulted in the selective nucleation of elongated α-Ga2O3 islands with a flat triangular cross-section on the window areas and their coalescence into a compact film. Transmission electron microscopy revealed that the dislocation density in the laterally grown area decreased drastically because the propagation of dislocations in the seed layer was effectively blocked by the mask. We believe these results greatly contribute to the realization of m-plane α-Ga2O3-based future power devices.