Highly reflective GaN/Al0.34Ga0.66N quarter-wave reflectors grown by metal organic chemical vapor deposition

Quarter-wave reflectors consisting of sets of GaN and ${\mathrm{Al}}_{\mathrm{0.34}}{\mathrm{Ga}}_{\mathrm{0.66}}\mathrm{N}$ layers have been grown on sapphire substrates by atmospheric-pressure metal organic chemical vapor deposition. A periodic structure with flat interfaces was observed by high-resolution scanning electron microscopy. X-ray diffraction measurements were performed to characterize the structures, from which the Al content x in the ${\mathrm{Al}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{N}$ layers was determined to be 0.34. No cracks could be seen on the surface of the reflectors by optical microscopy. The measured peak reflectivity at 390 nm increases with the number of pairs and reaches as high as $\text{96±2\%}$ in the 35-pair reflector.