Insight into the Ga/In flux ratio and crystallographic plane dependence of MBE self-assembled growth of InGaN nanorods on patterned sapphire substrates

Jian Shen; Yuefeng Yu; Jia Wang; Yulin Zheng; Yang Gan; Guoqiang Li

doi:10.1039/c9nr09767h

Insight into the Ga/In flux ratio and crystallographic plane dependence of MBE self-assembled growth of InGaN nanorods on patterned sapphire substrates

Nanoscale. 2020 Feb 14;12(6):4018-4029. doi: 10.1039/c9nr09767h. Epub 2020 Feb 4.

Authors

Jian Shen¹, Yuefeng Yu², Jia Wang³, Yulin Zheng², Yang Gan⁴, Guoqiang Li²

Affiliations

¹ State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China. [email protected] and School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, China. [email protected] and Center for Integrated Research of Future Electronics, and Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8601, Japan.
² State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China. [email protected] and Engineering Research Center on Solid-State Lighting and its Informationisation of Guangdong Province, South China University of Technology, Guangzhou 510640, China.
³ Center for Integrated Research of Future Electronics, and Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8601, Japan.
⁴ School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, China. [email protected].

PMID: 32016230
DOI: 10.1039/c9nr09767h

Abstract

A controllable self-assembled growth using molecular beam epitaxy (MBE) of dense, uniform, and high-aspect-ratio InGaN nanorods (NRs) is achieved through regulating the Ga/In flux ratio and employing high Miller index planes of patterned sapphire substrates (PSSs). It is clearly demonstrated that both the low Ga/In flux ratio and high Miller index plane of PSS patterns facilitate the three-dimensional growth mode for InGaN NRs and simultaneously suppress NR coalescence. A lower Ga/In flux ratio favors a higher density, a larger aspect ratio, and a smaller coalescence degree of InGaN NRs through enhancing axial growth and inversely suppressing radial growth. The specific surface structures of high Miller index planes, e.g., the well-organized step-terrace and irregular bulge structures, critically affect the morphology, dimensions, density, and crystallographic orientation of MBE self-assembled NRs. In particular, the narrow and ordered step-terrace structure in the C₃-plane-(4 5[combining macron] 1 38) plane-on a hexagonal pyramid favors the highest density, largest aspect ratio, and best uniformity of semipolar InGaN NRs, thus contributing to optimal photoluminescence performance. A thorough understanding of the mechanism of the effect of the Ga/In flux ratio and crystallographic plane on the MBE self-assembled growth behaviour of InGaN NRs was gained through experimental and theoretical exploration. This work contributes towards a deep understanding of the MBE self-assembled growth mechanism and controllable fabrication of dense, well-separated, and uniform InGaN NRs, thus contributing to the enhanced performance of NR-based optoelectronic devices.