Inversion domains triggering recovery of luminescence uniformity in epitaxially lateral overgrown thick GaN film

A 150 μm-thick GaN layer was grown by halide vapor phase epitaxy utilizing selective lateral overgrowth on a SiO₂-prepatterned sapphire substrate. A series of optically active regions above the SiO₂ mask was observed in cross sectional monochromatic cathodoluminescence images taken at 367 nm. These bright regions were, however, consistently terminated by triangular shaped domains at 60 to 80 μm thickness, leaving no sign of luminescence nonuniformity beyond the thickness. In conjunction with the recent results on the characteristics of inversion domains in GaN, we proposed that these triangular regions might be inversion domains.