Effect of sapphire substrate nitridation on determining rotation domain in GaN growth

Abstract

GaN films were grown at various V/III ratios on sapphire (0 0 0 1) substrates with and without nitridation process by radio-frequency plasma-excited molecular beam epitaxy. Based on the results of X-ray diffraction pole-figure and φ scan measurements, the GaN film grown without nitridation process has a tendency to form the metastable in-plane rotation domain by ∼11° from the substrate, in addition to the main domain rotated by 30° from the substrate. In suppressing the formation of the metastable in-plane rotation domain, it is found to be very effective to perform the nitridation process. In addition, even in GaN films grown without nitridation process, decrease in V/III ratio enables us to suppress the formation of the metastable domain. The rotation domains are considered to have the epitaxial relationship of [1 2 3 ̄ 0] GaN ∥[1 1 2 ̄ 0] sapphire and [ 1 ̄ 2 ̄ 3 0] GaN ∥[1 1 2 ̄ 0] sapphire .