Influence of cone-shaped pattern sapphire substrates on dislocation density and stress-strain of GaN epifilms by MOCVD

Abstract

GaN epifilms are grown on the 2.5 μm×1.6 μm×0.5 μm cone-shaped pattern sapphire substrates (CPSS) and unpattern planar sapphire substrates (USS) by MOCVD. High resolution X-ray diffraction (HRXRD) measurements show that the edge dislocation density of GaN epifilms on CPSS is less than on USS. From the transmission electron microscopy (TEM) observation, the CPSS can efficiently reduce the threading dislocation in GaN epilayer. The Raman scattering spectroscopy show that the CPSS can effectively decrease the residual stress in GaN epilayer. A strong and sharp PL band edge emission was observed for the GaN grown on CPSS compared to USS. The above result indicates the quality of GaN epilayers on CPSS is advantage to GaN epilayer on USS.