Growth of N-polar GaN on vicinal sapphire substrate by metal organic chemical vapor deposition

The growth and properties of N-polar GaN layers by metal organic chemical vapor deposition (MOCVD) were reported. It is found that N-polar GaN grown on normal sapphire substrate shows hexagonal hillock surface morphology. With the misorientation angles increasing from 0.5A degrees to 2.0A degrees toward the a-plane of the sapphire substrate, the number of the hillock becomes less and less and finally the surface becomes flat one on the sapphire substrate with the misorientation angle of 2A degrees. It is also found that the crystalline quality and the strain in the GaN are greatly influenced by the misorientation angle.