Influence of double AlN buffer layers on the qualities of GaN films prepared by metal?organic chemical vapour deposition

In this paper we report that the GaN thin film is grown by metal?organic chemical vapour deposition on a sapphire (0001) substrate with double AlN buffer layers. The buffer layer consists of a low-temperature (LT) AlN layer and a high-temperature (HT) AlN layer that are grown at 600 ?C and 1000 ?C, respectively. It is observed that the thickness of the LT-AlN layer drastically influences the quality of GaN thin film, and that the optimized 4.25-min-LT-AlN layer minimizes the dislocation density of GaN thin film. The reason for the improved properties is discussed in this paper.