Homoepitaxial Growth of GaN Nanorods via Irregular Masks
Chang-Hsun Huang1*, Wei-I Lee1, Yi-Chia Chou1
1Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
* Presenter:Chang-Hsun Huang, email:crazy78210@gmail.com
Gallium nitride (GaN), with wide direct bandgap of 3.4 eV as semiconductor, plays a crucial role in current optoelectronics and high-power electronic devices [1]. Compared with films of GaN, the rods of it permit more strain relaxation and possess large surface-to-volume ratio, which can be used for quantum-wells with core-shell structures to control light extraction with tunable bandgap [2]. Furthermore, GaN nanorods (NRs) with c-orientation provide non-polar and semi-polar facets for reducing the quantum-confined Stark effect (QCSE) and thus increase the emission efficiency and intensity of optical devices [3].
In this research, we propose a less complex and low cost approach using irregular masks for GaN NR fabrication on GaN substrate through hydride vapor phase epitaxy (HVPE) with a rapid growth rate. The grown GaN NRs are isolated by SiO2 islands, served as irregular masks, and the NRs grew along c-orientation with high aspect ratio and remarkably high density. By adjusting various growth parameters, the distinctive morphology and growth mechanism of the GaN NRs is examined. Furthermore, we demonstrate optical property and strain field of GaN NRs. The structural and optical properties of the GaN NRs are investigated by transmission electron microscopy (TEM), cathodoluminescence (CL), and photoluminescence (PL). The residual strain released in the grown GaN NRs is discovered by the Raman spectrum and TEM.

1. S. Nakamura. "The roles of structural imperfections in InGaN-based blue light-emitting diodes and laser diodes." Science 1998, 281, 956-961.
2. X. Wang et al. "Continuous-flow MOVPE of Ga-polar GaN column arrays and core–shell LED structures." Cryst. Growth Des. 2013, 13, 3475-3480.
3. H. P. T. Nguyen et al. "Controlling electron overflow in phosphor-free InGaN/GaN nanowire white light-emitting diodes." Nano Lett. 2012, 12, 1317-1323.

Keywords: GaN , nanorod, HVPE, homoepitaxy