Synthesis of homogeneous and high-quality GaN films on Cu(111) substrates by pulsed laser deposition

Abstract

GaN films were grown on Cu(111) substrates by growing an AlN buffer layer with an in-plane alignment of GaN[11−20]//AlN[11−20]//Cu[1−10] using pulsed laser deposition. It is found that by optimizing the laser rastering program and the epitaxial growth temperature, the thickness homogeneities, surface morphologies and structural properties of the GaN films can be greatly improved. Especially, the as-grown GaN films, grown at 750 °C with the optimized laser rastering program, exhibit excellent thickness uniformity with a root-mean-square (RMS) thickness inhomogeneity of less than 2.8%, and a very smooth and flat surface with a surface RMS roughness of 2.3 nm. The as-grown ~102 nm thick GaN films are almost fully relaxed with an in-plane compressive strain of only ~0.53%. No interfacial layer exists between the AlN buffer layer and the GaN film. Furthermore, with an increase in growth temperature from 550 to 750 °C, the surface morphologies and structural properties of the as-grown ~102 nm thick GaN films are improved significantly. The homogeneous and high-quality GaN films produced offer a broad prospect for future applications of GaN-based devices on Cu substrates.