The growth behaviors and high controllability of GaN nanostructures on stripe-patterned sapphire substrates

Abstract

The growth behaviors of multi-dimensional GaN nanostructures including simultaneous epitaxial growth of films and horizontal nanowires on the sapphire substrates were observed by making substrates per-patterned, leading to some interesting phenomena, thereby helping us understand the characteristics of GaN growth more comprehensively and clearly. The nonpolar a-plane GaN films grown on the Au-coated areas were formed by many triangular pyramids. And there are two kinds of GaN horizontal nanowires in the Au-free areas containing straight-growing nanowires and U-shaped nanowires. The detailed mechanism of those growth phenomena is proposed: when Au catalysts and Ga are sufficient, the growth of GaN is mainly controlled by vapor-solid (VS) mechanism, gradually growing into films. While when Au catalysts are insufficient, the growth of GaN mainly follows vapor-liquid-solid (VLS) mechanism. The difference between the growth of straight and U-shaped nanowires reflects that ±polarity has an important impact on the growth direction of nanowires, making the nanowires take an U-turn during the growth. In addition, the GaN nanostructures show a high degree of controllability. The width and length of nanowires, the continuity of films, even the presence of Au particles at the end of nanowires can be controlled, which provides a simple and convenient synthesis strategy.