Defect reduction in (112̄0) 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 $\text{(112̄0)}$ 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 ${\text{3×10}}^6\hspace{0.5em}{\mathrm{cm}}^{\text{−2}}$ compared to ${\text{∼10}}^{10}\hspace{0.5em}{\mathrm{cm}}^{\text{−2}}$ 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 ${10}^5\hspace{0.5em}{\mathrm{cm}}^{\text{−1}}$ and ${10}^9\hspace{0.5em}{\mathrm{cm}}^{\text{−2}},$ 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 ${\text{∼5×10}}^6\hspace{0.5em}{\mathrm{cm}}^{\text{−2}}$ and ${\text{3×10}}^3\hspace{0.5em}{\mathrm{cm}}^{\text{−1}},$ respectively.