title: Structural Anisotropy and Optical Properties of Nonpolar a-Plane GaN Epitaxial Layers.
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.
authors.forename: Yong Gon
authors.initials: YG
authors.lastname: Seo
authors.forename: Sun Hye
authors.initials: SH
authors.lastname: Shin
authors.forename: Doo Soo
authors.initials: DS
authors.lastname: Kim
authors.forename: Hyung-Do
authors.initials: HD
authors.lastname: Yoon
authors.forename: Sung-Min
authors.initials: SM
authors.lastname: Hwang
authors.forename: Kwang Hyeon
authors.initials: KH
authors.lastname: Baik