High quality GaN layers grown on slightly miscut sapphire wafers

HVPE grown layers typically show a high density of pyramidal structures on the surface. We found that a slight off-orientation of the substrate totally suppresses the development of these structures. Further we found that a misorientation toward the m-plane of GaN features a smoother surface morphology, compared to an off-orientation towards the a-plane. After the improvement of the surface morphology and other properties of the HVPE grown layers, we studied self-separation processes. Our approaches to remove the thick GaN-layer from the substrate were a low-temperature interlayer and a structured dielectric mask.