Effect of GaN template thickness and morphology on AlxGa1−xN (0 < x < 0.2) growth by MOVPE

We have grown AlxGa1−xN/GaN (0 < x < 0.2) films by MOVPE at atmospheric pressure in a home-made vertical reactor. The films were deposited on high temperature GaN templates which were grown on in situ nano-masked (0 0 0 1) sapphire substrates by using Si/N treatment. This process presents advantages of ELO technology without its ex situ complicated steps and induces a transition from 3D mode (initial stage) to 2D growth mode. We investigate systematically the effect of the template thickness and morphology on structural and morphological properties of AlGaN films. Four 0.5 μm-thick Al0.07Ga0.93N samples grown on different GaN templates have been studied. The HRXD and the AFM results show a better film quality when the AlGaN layer is grown on a 1.3 μm-thick 2D GaN template. It is possible to control the stress in the layers. The crystalline quality is also showed to degrade with Al solid content increase.