Realization of Controllable Growth of N-Polarity GaN Films on SiC Substrates by Modulating the Nucleation of the AlN Buffer Layer

Nitrogen-polarity (N-polarity) GaN films possess great potential in the preparation of high-performance high electron mobility transistors and long-wavelength light-emitting devices. Improving both the crystalline quality and surface morphology of N-polarity GaN films is crucial for the research and development of N-polarity nitride devices. In this work, we grew N-polarity GaN films on SiC substrates by metal–organic chemical vapor deposition. Meaningfully, we realize the controllable growth of N-polarity GaN films on SiC substrates by modulating the nucleation of the AlN buffer layer. The obtained N-polarity GaN films not only have a fine surface morphology but also possess a not-bad crystalline quality. Specifically, the root-mean-square roughness of the N-polarity GaN film over an area of 10 × 10 μm² is 1.68 nm, and the full width at half-maximum values of (0002) and (101̅2) planes X-ray diffraction rocking curves are 300 and 318 arcsec, respectively, corresponding to a threading dislocation density of ∼7.18 × 10⁸ cm^–2. Moreover, we propose a growth model of the N-polarity GaN film grown on the AlN buffer layer and analyze the mechanism by which the nucleation of AlN buffer layer affects the structural property of the N-polarity GaN film. This work presents a method for obtaining high-quality N-polarity GaN films on SiC substrates, which is beneficial for promoting the research and development of N-polarity nitride devices.