Impact of H2-preannealing of the Sapphire Substrate on the Crystallization of Low-Temperature-Deposited AlN Buffer Layer

ABSTRACTThe effect of H2-preannealing of sapphire substrate on low-temperature (LT- ) AlN buffer layer deposited by metalorganic vapor phase epitaxy is investigated. Crystallinity of LT-AlN drastically changes with preannealing temperature variation. It is found that H2-preannealing of sapphire substrate is a requisite to get a better quality LT-AlN and as a consequence it leads to growth of better quality GaN epi-layer on it.