Growth and Characterization of GaN Nanowires for Hydrogen Sensors JASON L. JOHNSON, 1 YONGHO CHOI, 1 ANT URAL, 1,4 WANTAE LIM, 2 J.S. WRIGHT, 2 B.P. GILA, 2 F. REN, 3 and S.J. PEARTON 2 1.—Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL 32611, USA. 2.—Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611, USA. 3.—Department of Chemical Engineering, University of Florida, Gainesville, FL 32611, USA. 4.—e-mail: antural@ufl.edu We report on the growth and characterization of high-quality GaN nanowires for hydrogen sensors. We grew the GaN nanowires by catalytic chemical vapor deposition (CVD) using gold thin films as a catalyst on a Si wafer with an insulating SiO 2 layer. Structural characterization of the as-grown nanowires by several methods shows that the nanowires are single-crystal wurtzite GaN. Photoluminescence measurements under 325 nm excitation show a near-band-edge emission peak around 3.4 eV. The hydrogen sensors are fabricated by contacting the as-grown GaN nanowires by source and drain electrodes and coating them with a thin layer of Pd. Hydrogen sensing experiments using the fabricated devices show high sensitivity response (ppm detection limit at room temperature) and excellent recovery. This work opens up the possibility of using high-quality GaN nanowire networks for hydrogen sensing applications. Key words: GaN nanowire, hydrogen sensor, chemical vapor deposition INTRODUCTION Nanowires have attracted significant research attention in recent years due to their unique structural, electronic, optical, and mechanical properties. 1,2 These properties make nanowires promising building blocks for potential applications such as transistors, lasers, photodetectors, and chemical and biological sensors. There has also been significant recent interest in the development of hydrogen sensors 3–5 for use in fuel cells as an energy source to replace petroleum. Since hydrogen is a hazardous, odorless, and highly flammable gas, hydrogen gas sensors play a critical role, particularly for fuel leak detection in space- craft, automobiles, and aircraft, fire detectors, and diagnosis of exhaust and emissions from industrial processes. 5–9 Nanowires are becoming promising candidates for H 2 gas sensors due to their high surface-to-volume ratio. 3,10–12 Wide-bandgap semiconductors such as GaN and ZnO have excellent potential for H 2 gas sensing because of their sensitivity to surface charge and ability to operate over large temperature ranges. 3,10,13,14 In addition, the use of a metallic coating can functionalize the surface of nanowires by dissociating H 2 into atomic hydrogen. While H 2 sensors based on nanowires such as ZnO, SnO 2 , and In 2 O 3 with excellent response and recovery charac- teristics have been reported in the literature, 10,14,15 there have been few reports on H 2 gas sensors based on GaN nanowires, which should offer excellent environmental stability. In this paper, we report on the growth and char- acterization of GaN nanowires for hydrogen sen- sors. The GaN nanowires were grown by a catalytic chemical vapor deposition (CVD) approach using Au thin films as a catalyst on a Si wafer with an insu- lating SiO 2 layer. The structural characterization of the as-grown nanowires by several methods shows (Received July 23, 2008; accepted October 24, 2008; published online November 19, 2008) Journal of ELECTRONIC MATERIALS, Vol. 38, No. 4, 2009 Special Issue Paper DOI: 10.1007/s11664-008-0596-z Ó 2008 TMS 490