GaN metal-semiconductor-metal (MSM) ultraviolet photodetectors with antimony-doped tin oxide (ATO) transparent electrodes were fabricated and characterized. The ATO films with the thickness of 750 nm were deposited on GaN substrates by RF magnetron sputtering. The main. X-ray peak of ATO film was identified as (101) using the X-ray diffraction (XRD) technique. The barrier height between ATO and GaN was determined to be 1.12 eV. Finally, the responsivity of undoped GaN-based MSM photodetectors with ATO electrodes measured at 325 nm under the bias voltage of 1 and 5 V was 0.051 and 0.095 A W-1, respectively. (c) 2006 Elsevier B.V. All rights reserved.