MOCVD growth of AlN/GaN DBR structures under various ambient conditions

Abstract

The high-reflectivity AlN/GaN distributed Bragg reflector (DBR) structures were realized by metal organic chemical vapor deposition (MOCVD) growth under pure N 2 ambient for AlN epilayer growth. The highest peak reflectivity of about 94.5% with a stopband width of 18 nm at a center wavelength of 442 nm was obtained. For the DBR structure with AlN layer grown under mixture of N 2/H 2 and pure H 2 conditions, the center wavelength was blue-shifted to 418 and 371 nm and the peak reflectivity also showed a reduction to 92% and 79%, respectively. The stopband width also decreases with increasing H 2 contents. The surface roughness and the grain size of the grown DBR structures showed an increase with increasing the H 2 ambient gas ratio. For realization of a high reflectivity and broad bandwidth of AlN/GaN DBR by using the MOCVD growth method, the pure N 2 ambient gas for growth of AlN layer should be preferable and optimal condition.