Epitaxial lateral overgrowth of off-basal GaN thin-film growth orientations

Non-polar (1 1 2¯ 0) and semi-polar (1 1 2¯ 2) GaN thin films were grown heteroepitaxially on r-plane and m-plane sapphire, respectively. As-grown films suffered from a high density of defects. Epitaxial lateral overgrowth was shown to be an effective technique for lowering the defect density when stripes of masking material were oriented along the in-plane GaN m-axis for both (1 1 2¯ 0)- and (1 1 2¯ 2)-oriented films. Parallel stripes of SiOx 5 μm wide with 5 μm spacing were fabricated using traditional wet-chemistry photolithography, and subsequent regrowth occurred through the window regions and over the mask. Growth-related extended defects terminate at the interface with the mask, and are absent in overgrown material where dislocation formation and propagation are limited. A novel double-processing technique was attempted on (1 1 2¯ 0)-oriented GaN by initially regrowing to create high-aspect features in the window, and then depositing SiOx on top of the mesas. Further regrowth occurred over both sets of masks, to produce a continuous film across the entire wafer.