Low-dislocation-density GaN from a single growth on a textured substrate

The density of threading dislocations (TD) in GaN grown directly on flat sapphire substrates is typically greater than 109/cm2. The density of dislocations can be decreased by orders of magnitude using cantilever epitaxy, which employs pre-patterned sapphire substrates to provide reduced-dimension mesa regions for nucleation and etched trenches between them for suspended lateral growth of GaN or AlGaN. The substrate is pre-patterned with narrow lines and etched to a depth that permits coalescence of laterally growing III–N nucleated on the mesa surfaces before vertical growth fills the etched trench. Low-dislocation densities typical of epitaxial lateral overgrowth are obtained in the cantilever regions and the TD density is also reduced up to 1 μm from the edge of the support regions.