A new "three-step method" for high quality MOVPE growth of III-nitrides on sapphire

A new "three-step method" was developed to grow high-quality III-nitrides by LP-MOVPE. The first step is composed of nitridation of sapphire substrate and growth of thin AIN laver by a migration enhanced method at high temperature of 1100 degreesC. The second step included a TMAI preflow and subsequent deposition of low temperature GaN buffer laver. The TMAI preflow was introduced at the buffer laver growth temperature to make at least a 2ML coverage on AIN surface, which served to obtain GaN buffer laver with Ga polarity. The third step was to grow epilayer at 1080 degreesC. The mechanisms for quality improvement were discussed. It was proved that the three-step method could be a new approach to grow high quality epilayers on large-lattice-mismatched substrates.