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

Abstract

High reflectivity AlN/GaN DBR structures were grown by MOCVD under three ambient gas conditions during the AlN layer growth. Highest peak reflectivity of about 94.5% with a stopband width of 18 nm at a center wavelength of 442 nm was obtained under pure N2 gas ambient growth condition. The center wavelength of the DBR structures blue-shifted to 418 nm and 371 nm and the peak reflectivity also showed a reduction to 92% and 79% under the ambient gas conditions of a N2/H2 mixture and pure H2 respectively. Surface roughness showed slight increase from 8 nm to 12 nm, and the groove depth shows an increase from 25 nm to 60 nm with increasing the H2 ambient gas ratio. TEM results showed that AlN grown rate was reduction with the increasing H2 content in the ambient gas. The simulation result indicated that optical loss of AlN layers was increased from 450 cm-1 to 1850 cm-1 with the increasing H2 content in the ambient gas.