Highly Controllable Epitaxial Growth of High-Density Nonpolar GaN Nanorod Arrays

Abstract

The undesirable effects of the degraded device performance and shorter lifetime caused by the polarization electric field induced by polar GaN have contributed to an increasing interest in the fundamental research and promising applications of nonpolar GaN. Herein, we demonstrate a strategy to construct high-quality arrays of well-aligned nonpolar GaN nanorods on the Au-coated (100) γ-LiAlO 2 substrates by the chemical vapor deposition method. During the growth process, the Au particles that were originally at the tips of the nanorods were found to gradually disappear with time. The disappearance of Au particles solved the problem of catalyst contamination and also demonstrated an interesting growth mechanism: whereas the traditional vapor−liquid− solid dominated the initial growth stage, the Au catalyst began to migrate and detach under the relatively Ga-rich condition, and then the vapor−solid controlled the subsequent growth. The E 2 (high) phonon peak (567.7 cm −1 ) and the strong ultraviolet emission peak (362.0 nm) indicate that the nonpolar GaN nanorods are virtually strain-free and have a high crystallization quality. Additionally, the effects of NH 3 and the thickness of Au films on the growth of GaN nanorods were thoroughly investigated. The well-arranged nonpolar GaN nanorod arrays with excellent crystal quality will provide a referable nanomaterial choice for highperformance, high-efficiency nonpolar nanodevices.