M -plane GaN grown on m-sapphire by metalorganic vapor phase epitaxy

GaN layers have been grown on m-plane sapphire by metal organic vapor phase epitaxy using low-temperature AlN nucleation layers. Depending on substrate nitridation and annealing treatments prior to depositing the nucleation layer, the crystal orientation of the resulting GaN layer may be either (11−22) or (1−100) (m plane). For suitably controlled conditions, GaN epilayers with a single m-plane orientation are reproducibly obtained as confirmed by x-ray diffraction. There is a 90° in-plane rotation of the epilayer such that the GaN a axis is parallel to the sapphire c axis.