Impact of H 2 -Preannealing of the Sapphire Substrate on the Crystallinity of Low-Temperature-Deposited AlN Buffer Layer

Effect of H 2 -preannealing of sapphire substrate on low-temperature-deposited (LT) AlN buffer layer deposited by metalorganic vapor epitaxy has been investigated. Crystallinity of LT-AlN buffer layer drastically changes with preannealing temperature variation. It is found that H 2 -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.