Influence of sapphire annealing in trimethylgallium atmosphere on GaN epitaxy by MOCVD

The ratio between N and Ga polarity in the deposited GaN layers can be adjusted by means of changing the annealing time in TMG atmosphere of the sapphire substrate. For an annealing time of 20 min the layers are completely N-polar and for a time of 60 min Ga polar epilayer are grown.