Effect of Slight Misorientation of Sapphire Substrate on Metalorganic Chemical Vapor Deposition Growth of GaN

The effects of slight misorientation from c -plane (0001) sapphire (α-Al 2 O 3 ) substrates on GaN surface morphologies and electroluminescence (EL) properties were studied. The GaN layers were grown using a two-step growth method under atmospheric pressure by metalorganic chemical vapor deposition (MOCVD). When using around 0.17° misoriented sapphire substrate tilted toward both <1120> and <1100> directions, a small step-type morphology appeared. On the other hand, using c -plain substrate or substrates with the misorientation angle larger than approximately 0.25° from the c -plane, a scale-shaped morphology appears. We also found that the misorientation of the substrate significantly affects the uniformity of the EL image. On the other hand, the light output powers of the light-emitting diodes (LEDs) fabricated on the substrates with different misorientations were almost the same in spite of the different surface morphologies.