Open Access Nano Express

Large-scale and uniform preparation of pure-phase wurtzite GaAs NWs on non-crystalline substrates

Ning Han1, Jared J Hou1, Fengyun Wang1, SenPo Yip1, Hao Lin1, Ming Fang1, Fei Xiu1, Xiaoling Shi1, TakFu Hung1 and Johnny C Ho12*

Author Affiliations

1 Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Ave., Hong Kong, SAR 999077, China

2 Centre for Functional Photonics (CFP), City University of Hong Kong, 83 Tat Chee Ave., Hong Kong, SAR 999077, China

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Nanoscale Research Letters 2012, 7:632  doi:10.1186/1556-276X-7-632

Published: 21 November 2012

Abstract

One of the challenges to prepare high-performance and uniform III-V semiconductor nanowires (NWs) is to control the crystal structure in large-scale. A mixed crystal phase is usually observed due to the small surface energy difference between the cubic zincblende (ZB) and hexagonal wurtzite (WZ) structures, especially on non-crystalline substrates. Here, utilizing Au film as thin as 0.1 nm as the catalyst, we successfully demonstrate the large-scale synthesis of pure-phase WZ GaAs NWs on amorphous SiO2/Si substrates. The obtained NWs are smooth, uniform with a high aspect ratio, and have a narrow diameter distribution of 9.5 ± 1.4 nm. The WZ structure is verified by crystallographic investigations, and the corresponding electronic bandgap is also determined to be approximately 1.62 eV by the reflectance measurement. The formation mechanism of WZ NWs is mainly attributed to the ultra-small NW diameter and the very narrow diameter distribution associated, where the WZ phase is more thermodynamically stable compared to the ZB structure. After configured as NW field-effect-transistors, a high ION/IOFF ratio of 104 − 105 is obtained, operating in the enhancement device mode. The preparation technology and good uniform performance here have illustrated a great promise for the large-scale synthesis of pure phase NWs for electronic and optical applications.

Keywords:
GaAs nanowires; Wurtzite phase; Non-crystalline substrates; P-type semiconductors; 61.46.Km; 73.63.Nm; 78.40.Fy