HVPE growth of self-aligned GaN nanorods on c-plane, a-plane, r-plane, and m-plane sapphire wafers

• Published in: Journal of materials science Vol. 50; no. 19; pp. 6260 - 6267
• Main Authors: Ryu, Sung Ryong, Gopal Ram, S. D, Kwon, Yang Hae, Yang, Woo Chul, Kim, Seung Hwan, Woo, Yong Deuk, Shin, Sun Hye, Kang, Tae Won
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.10.2015; Springer; Springer Nature B.V
• Subjects: Alignment; Anomalies; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Crystallography; Crystallography and Scattering Methods; Epitaxy; Excitation; Gallium nitrides; hydrides; Liquors; Materials Science; Nanorods; orientation; Original Paper; Photoluminescence; Polarizers; Polymer Sciences; Sapphire; Self alignment; Solid Mechanics; Substrates; Vapor phase epitaxy; Vapor phases; vapors; Vertical orientation; Hydride Vapor Phase Epitaxy; Surface Optical; Sapphire; Sapphire Substrate; GaCl3
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-015-9146-2

Herein, we report the self-aligned growth of GaN nanorods on different orientations of sapphire like c-, a-, r- and m-plane substrates by hydride vapor phase epitaxy. Vertical c-axis orientation of GaN NRs is obtained on c-plane [0001] and a-plane [Formula: see text] sapphire and a skew or inclined NRs on r-plane, and inclined intertwined but self-aligned NR array was formed on m-plane sapphire. GaN (002) and (004) peaks were obtained on c- and a-plane sapphire, whereas (110), (103), and (103) only were observed on r- and m-planes, respectively. In the case of r- and m-plane-grown GaN, A₁ transverse optical mode is dominant, and the A₁ longitudinal optical mode is suppressed. Conversely, in the case of c- and a-plane, it is reversed. The probable reason is the optical mode vibrations difference along the differently inclined NRs surfaces. In addition, the specimen exhibits surface optical modes too. The optical behavior of GaN NR on m-sapphire shows an intensity variation when measured in different angular rotations of the specimen by photoluminescence which is because of the higher area of excitation in the case of axial surfaces and lower area of excitation in radial surface. Their epitaxial crystallographic relationship with the substrates and the reasons for the self-aligned orientations are discussed. The anomalies found in the optical behavior are attributed to Raman antenna effect and so on. The self-aligned intertwined GaN NRs find suitable applications in polarizer.