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

• Reports on AlN/GaN DBRs on SiC substrate were grown by MBE before, while our DBRs were grown by MOVPE method in this work.
• A 30 pairs of AlGaN/GaN DBRs with high reflectance (>92%) were obtained, while theoretical calculation result is 93%.
• Optical microscopy shows that the AlGaN/GaN DBRs are free of cracks by inducing AlN/AlGaN double buffer layers.
• AFM shows the RMS surface roughness of AlGaN/GaN DBRs with double buffer layers is low and corresponds to 2.0 nm.
• The DBRs with smooth surfaces are necessary to grow a high quality RC LEDs, photodetectors, or VCSELs in UV region.

Ultraviolet AlGaN/GaN distributed Bragg reflectors (DBRs) were grown on 2 in. Si-face 6H-SiC(0 0 0 1) 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 395 nm with a FWHM at 14 nm.