Impacts of specific element-treated three-dimensional GaN layer on characteristics of nonpolar a-plane GaN film

Abstract

Nonpolar a-plane GaN films with three-dimensional (3D) GaN layers have successfully grown on r-plane sapphire substrates by metal organic chemical vapor deposition. The inserted 3D GaN layers were grown accompanied with the treatment by various kinds of elements such as Si, Mg, and In to further improve the characteristics of the subsequently lateral overgrown nonpolar a-plane GaN films. Scanning electron microscopy, x-ray rocking curve, and room temperature photoluminescence spectroscopy were used to examine the effects of the introduction of the specific element-treated 3D GaN layer on the crystalline quality, the anisotropy, and the optical property of the nonpolar a-plane GaN film. It was found that significant improvements in the crystalline quality and optical property as well as a remarkable reduction in anisotropy have been achieved for the nonpolar a-plane GaN film grown on the r-plane sapphire substrate by inserting a 3D GaN layer treated with Si. In fact, evident reduction in full width at half maximum of x-ray rocking curves from 972 to 651 arcsec along the c-axis (φ = 0°) and from 1234 to 752 arcsec along the m-axis (φ = 90°), and a notable decrease in anisotropy from 27.0% to 15.6% were obtained with the employment of Si treatment to the 3D GaN layer.

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

“…The difference in electronegativity leads to the formation of electric dipoles, which in turn results in spontaneous polarization. In order to avoid/overcome the polarization effect caused by the polar GaN, the research focusing on the growth of nonpolar GaN is gradually increasing, with one-dimensional nanomaterials being a significant component. − One-dimensional nanomaterials such as nanowires and nanorods are considered as promising candidates for next-generation high-performance devices because of their huge surface–volume ratio and highly regulable structure compared to bulk GaN crystal materials. , Various growth techniques have been applied to the growth of nonpolar GaN nanowires, including metal-catalyzed metal-organic chemical vapor deposition (MOCVD), direct nitridation/vapor transport, , and catalyst-free selective-area molecular beam epitaxy (SA-MBE) . And among the increasingly sophisticated preparation systems, the convenient chemical vapor deposition (CVD) method is one representative of the ways to prepare nanomaterials.…”