Effects of defects on the morphologies of GaN nanorods grown on Si (111) substrates
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Young Hae Kwon and Tae Won Kang Quantum Functional Semiconductor Research Center, Dongguk University, Seoul 100-715, Korea
Joo Hyung You, Dea Uk Lee, and Taewhan Kima) National Research Laboratory for Nano Quantum Electronics Devices, Department of Electronics and Communications Engineering, Hanyang University, Seoul 133-791, Korea (Received 27 April 2009; accepted 3 August 2009)
Scanning electron microscopy and transmission electron microscopy images and selected area electron diffraction pattern showed that the one-dimensional GaN nanorods with [0001]-oriented single-crystalline wurzite structures were formed on Si (111) substrates by using hydride vapor-phase epitaxy without a catalyst. Although some stacking faults and inversion domain boundaries existed in the GaN nanorods, few other defects such as threading dislocations were observed. The formation of the facet plane in the N-polar region of the GaN nanorod containing an inversion domain boundary originated from the slow growth rate, followed by the lateral adatom diffusion from the Ga-polar region to reduce the length difference.
I. INTRODUCTION
Wide-energy-gap compound semiconductors have become particularly attractive because of interest in their promising applications in optoelectronic devices, such as light-emitting diodes and lasers,1–4 operating in the visible-ultraviolet region of the spectrum. Because commercial GaN substrates are not available yet, GaN thin films or one-dimensional (1-D) nanostructures are grown on hetero-substrates, such as Al2O3, Si (111), or 6H–SiC substrates.5–7 GaN thin films contain a high density of defects, such as threading dislocations, because of the large lattice mismatch and the large difference thermal expansion coefficients between the GaN thin film and the substrate.8,9 The dislocations existing in GaN materials and their related materials are typically trap centers, leakage current sources, and impurity diffusion paths.10,11 Even though many studies have been carried out to obtain high-quality GaN materials,12,13 the most desirable way to obtain high-quality GaN materials is the formation of single-crystal GaN nanostructures containing low defects, such as nanowires and nanorods.14,15 High-quality 1-D GaN materials have drawn a great deal of interest because of many potential applications, such as 1-D laser and nanomanipulation tools16 and a substitution of conventional application of GaN thin films. Various synthesis methods such as metal-organic chema)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0391
3032
http://journals.cambridge.org
J. Mater. Res., Vol. 24, No. 10, Oct 2009 Downloaded: 14 Mar 2015
ical vapor deposition17 and molecular beam epitaxy18 have been performed to obtain high-quality 1-D GaN nanostructures. Although hydride vapor-phase epitaxy (HVPE) has excellent advantages such as high growth rate and low growth cost, this method is relatively little used to grow 1-D GaN nanostructures because of the inherent difficulties of the precise precursor
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