The high-reflectivity AlN/GaN distributed Bragg reflector (DBR) structures were realized by metal organic chemical vapor deposition (MOCVD) growth under pure N2 ambient for AlN epilayer growth. The highest peak reflectivity of about 94.5% with a stopband width of 18nm at a center wavelength of 442 nm was obtained. For the DBR structure with AlN layer grown under mixture of N2/H2 and pure H2 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 H2 contents. The surface roughness and the grain size of the grown DBR structures showed an increase with increasing the H2 ambient gas ratio. For realization of a high reflectivity and broad bandwidth of AlN/GaN DBR by using the MOCVD growth method, the pure N2 ambient gas for growth of AlN layer should be preferable and optimal condition.
- Ambient gas
- Distributed Bragg reflector