AlN/GaN Distributed Bragg Reflectors Grown via Metal Organic Vapor Phase Epitaxy using GaN Insertion Layers

摘要

Distributed Bragg Reflectors (DBRs) are an important component of various optoelectronic devices for ultra violet and visible wavelengths. In the Ill-Nitride material system, Aluminum Nitride (AlN) and Gallium Nitride (GaN) offer a large contrast in refractive index and are therefore well suited for fabricating DBRs with high reflectivity and wide bandwidths using relatively few periods. However, the large lattice and thermal mismatch leads to cracking in these heterostructures. In this work short period superlattice layers have been used to fabricate high reflectivity (> 94%) nitride based DBRs via Metal Organic Vapor Phase Epitaxy. Short period AlN/GaN superlattices containing three to four monolayers of GaN have been employed as the low refractive index layer in DBRs to minimize cracking. Using this technique, crack-free DBRs reflecting from 440-475 run with up to 25 periods have been fabricated. The technique has been proven to be versatile and resulted in large area yield DBRs grown on a variety of different sapphire substrates.