Wing-tilt-free gallium nitride laterally grown on maskless chemical-etched sapphire-patterned substrate

A method is developed to overcome the problem of wing tilt that appears in lateral epitaxial overgrowth of GaN films. High-quality GaN films free of wing tilt were obtained reproducibly on wet chemical-etched maskless c-plane sapphire substrate using metalorganic chemical vapor deposition (hereafter called CantiBridge epitaxy). Symmetrical (0002) x-ray diffraction of a4.5-μm-thick GaN film is performed with the scattering plane parallel and perpendicular to the stripe direction. The corresponding full widths at half maxima of the (0002) peaks are about 147 and 144 arcsec, respectively, which is one of the best results reported to date. Scanning electron microscopy cross-section images show that GaN was selectively grown on the mesas and the lateral overgrowth GaN spanned the etched trenches. No GaN was found on the grooved sapphire trenches, which is very different from the usually observed phenomena in other lateral epitaxial overgrowth techniques. It is inferred that damage-free mesas and grooves benefit the elimination of wing tilt and they improve the quality of the lateral overgrown GaN. The results indicate that CantiBridge epitaxy is a promising technique for fabricating high-quality GaN-based materials and devices.