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In-situ reflectance monitoring and characterization of GaN grown by MOCVD

Despite rapid progress in the development of optoelectronic and electronic devices based on wide bandgap III-nitride semiconductors, growth of GaN by MOCVD (by far the most effective means of GaN material synthesis) has remained largely a "black-box" process. The optimization and exploration of the vast parameter space has depended solely on ex-situ characterization with growth recipes to a great extent confined to the so called "two-step" nucleation procedure first proposed by Akasaki et. al. We showed previously that, due to a well-behaved, laminar gas flow pattern in the high-speed rotating-disk MOCVD reactor, it is possible to avoid undesirable coatings and to preserve optical access to the growth surface. An in-situ optical reflectometer was employed in this work to probe and extract information such as growth rates, deposition uniformity, and morphological evolution during the initial hetero-nucleation of GaN on sapphire.