Controlled growth of gallium nitride single-crystal nanowires using a chemical vapor deposition method
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Controlled growth of gallium nitride single-crystal nanowires using a chemical vapor deposition method Song Han, Wu Jin, Tao Tang, Chao Li, Daihua Zhang, and Xiaolei Liu Department of Electrical Engineering—Electrophysics, University of Southern California, Los Angeles, California 90089-0271
Jie Han Eloret Corporation, NASA Ames Research Center, Mountain View, California 94035
Chongwu Zhoua) Department of Electrical Engineering—Electrophysics, University of Southern California, Los Angeles, California 90089-0271 (Received 10 September 2002; accepted 28 October 2002)
Chemical vapor deposition (CVD) using gold nanoparticles as the catalyst to grow high-quality single-crystal gallium nitride nanowires was developed. This method enables control over several important aspects of the growth, including control of the nanowire diameter by using monodispersed gold clusters, control of the nanowire location via e-beam patterning of the catalyst sites, and control of the nanowire orientation via epitaxial growth on a-plane sapphire substrates. Our work opens up new ways to use GaN nanowires as nanobuilding blocks. During the past few years, increasingly more effort has been devoted to the research on III–V nitride semiconductors because of their exciting properties.1,2 GaN is particularly interesting among III–V nitrides, as its large band gap (3.4 eV), large dielectric breakdown field, superior electron transport properties, and good thermal conductivity make it ideal for high-power/hightemperature electronic applications. In addition, GaN is also used as an important optoelectronic material because of its direct band gap in the blue light-emitting regime. Success in growing high-quality GaN thin films has led to the demonstration of a family of novel devices such as blue light-emitting diodes,3 laser diodes,4 zerodimension quantum dots,5 and two-dimension quantum wells.6,7 In contrast, controlled synthesis of GaN nanowires of predetermined diameters and/or at predetermined sites is still limited,8,9 even though this can be important for nanoscale optoelectronic applications. Synthesis of GaN nanowires has been attempted by a number of groups using various techniques such as laser ablation of GaN-containing targets,10,11 arc discharge,12 nanotube-confined reaction of Ga/Ga2O3 with NH3,13 reaction of Ga/Ga2O3 mixture with NH3 in anodic alumina templates,14 and thermal chemical vapor deposition
a)
Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 18, No. 2, Feb 2003
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(CVD) from Ga-containing precursors and NH3.15–21 The laser ablation 10,11 and CVD 15–21 methods are particularly interesting because they exploit the vapor– liquid–solid (VLS) growth mechanism,10 where In, Fe, Ni, and Co nanoparticles have been used as the catalyst. One common feature of the above-mentioned work is that growth of GaN nanowires of predetermined diameters has not been achieved, presumably because of the difficulty associated with producing monodisper
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