  High-reflectance group III-nitride distributed Bragg reflectors (DBRs) were
deposited by MOCVD on Si (111) substrates. A reflectance greater than 96% was
demonstrated for the first time for an AlN/GaN DBR with a stop-band centered in
the blue-green range of the visible spectrum. Crack-free GaN cap layers were
grown on the DBR structures to demonstrate the opportunity to build III-nitride
optoelectronic devices in this material. The DBR structure was under
significant strain due to growth on a mismatched substrate although the GaN cap
layer was shown to be strain free.
