Defect reduction in (1120) a-plane gallium nitride via lateral epitaxial overgrowth by hydride vapor-phase epitaxy

This letter reports on the reduction in extended-defect densities in a-plane (112̄0) GaN films achieved via lateral epitaxial overgrowth (LEO) by hydride vapor phase-epitaxy. A variety of dielectric mask patterns was used to produce 8–125-μm-thick, fully coalesced nonpolar GaN films. The nanometer-scale pit densities in the overgrown regions were less than 3×106 cm−2 compared to ∼1010 cm−2 in the direct-growth a-plane GaN. Cathodoluminescence revealed a fourfold increase in luminous intensity in the overgrown material compared to the window material. X-ray rocking curves indicate the films were free of wing tilt within the sensitivity of the measurements. Whereas non-LEO a-plane GaN exhibits basal plane stacking fault and threading dislocation densities of 105 cm−1 and 109 cm−2, respectively, the overgrown LEO material was essentially free of extended defects. The basal plane stacking fault and threading dislocation densities in the wing regions were below the detection limits of ∼5×106 cm−2 and 3×103 cm−1, respectively.