J Nanosci Nanotechnol. 2015 Oct;15(10):7787-90. doi: 10.1166/jnn.2015.11188.

Structural Anisotropy and Optical Properties of Nonpolar a-Plane GaN Epitaxial Layers.

Journal of nanoscience and nanotechnology

Yong Gon Seo, Sun Hye Shin, Doo Soo Kim, Hyung-Do Yoon, Sung-Min Hwang, Kwang Hyeon Baik

PMID: 26726413 DOI: 10.1166/jnn.2015.11188

Abstract

In-plane structural anisotropy is characteristic of nonpolar (1120) a-plane GaN (a-GaN) films grown on r-plane sapphire substrates. The anisotropic peak broadenings of X-ray rocking curves (XRCs) are clearly observed with M- or W-shaped dependence on the azimuth angles. We investigated the optical properties of both M- and W-shaped a-GaN samples with room and low-temperature photoluminescence (PL) measurements. The W-shaped a-GaN film showed higher PL intensity and more compressive strain compared to the M-shaped a-GaN film, whereas the XRC peak widths of the M-shaped a-GaN film on the azimuth angles are lower than those of W-shaped specimens, indicating that better crystalline quality was obtained. We speculate that the PL intensity and strain state of a-GaN layers may be more influenced by the crystallinity of a specific crystal orientation or direction, especially along the m-axis as opposed to the c-axis. This occurrence is most likely due to anisotropic defect distributions, resulting from differences in dangling bond densities of (0001) and {1-100} facets.

Publication Types

• Journal Article
• Research Support, Non-U.S. Gov't