Microstructure of nitrides grown on inclined c-plane sapphire and SiC substrate

Abstract

High-quality ( 1 1 2 ¯ 0 ) GaN layers with atomically flat surface have been grown on a precisely offset-angle-controlled ( 1 1 ¯ 0 2 ) sapphire substrate by metal-organic vapor phase epitaxy (MOVPE). Insertion of AlGaN layer between underlying AlN layer and GaN was found to improve crystalline quality of upper GaN layer. In addition, a combination of high growth condition followed and epitaxial lateral overgrowth has been employed for the growth of GaN and this helped in reducing the dislocation density in the resultant layers. GaN and AlN were grown on ( 3 0 3 ¯ 8 ) SiC substrates by MOVPE and sublimation methods, respectively. The crystal orientation of GaN and AlN could be just aligned to that of the substrate. Microstructure analysis of the layers was also carried out by transmission electron microscopy.