Effect of the thickness of InGaN interlayer on a-plane GaN epilayer**Project supported by the National Natural Science Foundation of China (Grant Nos. 91233111, 61274041, and 11275228), the Special Funds for Major State Basic Research Project of China (Grant No. 2012CB619305), the National High Technology R & D Program of China (Grant Nos. 2014AA032603 and 2014AA032609), and the Guangdong Provincial Special

Abstract

In this paper, we use the a-plane InGaN interlayer to improve the property of a-plane GaN. Based on the a-InGaN interlayer, a template exhibits that a regular, porous structure, which acts as a compliant effect, can be obtained to release the strain caused by the lattice and thermal mismatch between a-GaN and r-sapphire. We find that the thickness of InGaN has a great influence on the growth of a-GaN. The surface morphology and crystalline quality both are first improved and then deteriorated with increasing the thickness of the InGaN interlayer. When the InGaN thickness exceeds a critical point, the a-GaN epilayer peels off in the process of cooling down to room temperature. This is an attractive way of lifting off a-GaN films from the sapphire substrate.