Misorientation-angle dependence of GaN layers grown on a-plane sapphire substrates by metalorganic chemical vapor deposition

High-quality GaN with smooth surface morphology has been grown on vicinal a-plane sapphire substrates by metalorganic chemical vapor deposition. The misorientation angles of vicinal a-plane sapphire substrates were changed systematically and the results were compared with the growth on exact a- and c-plane sapphire substrates. Surface morphology and crystalline qualities are found to be very sensitive to misorientation angles of a-plane sapphire substrates and the misorientation angle was optimized to be 0.25°.