Crack-free ultraviolet AlGaN/GaN distributed Bragg reflectors grown by MOVPE on 6H-SiC(0 0 0 1)

Abstract

Ultraviolet AlGaN/GaN distributed Bragg reflectors (DBRs) were grown on 2in. Si-face 6H-SiC(0001) by metal organic vapor phase epitaxy (MOVPE). Two samples with single AlGaN buffer layer and AlN/AlGaN double buffer layers were introduced to grow AlGaN/GaN DBRs. The optical microscope images show that there are plenty of cracks on the surface of the DBR with single AlGaN buffer. While for DBR with AlN/AlGaN double buffer layer are free of cracks. A 30 period of Al0.2Ga0.8N/GaN DBR was obtained with measured reflectance of over 92%. The crack-free DBR has a stop-band centered around 395nm with a FWHM at 14nm.