GaN Metal-Semiconductor-Metal Visible-Blind Photodetectors with Transparent Indium-Tin-Oxide Contact Electrodes

Abstract

Indium-tin-oxide (ITO) layers were deposited onto n-GaN films by DC magnetron sputtering and GaN metal-semiconductor-metal (MSM) photodetectors were fabricated. The Schottky barrier height of ITO on n-GaN was determined to be approximaately 0.80 eV. The ITO contacts on n-GaN have lower dark currents compared with other metals, Au, Pd and Ni. It was also found that we could achieve a photocurrent-to-dark-current contrast higher than two orders of magnitude by applying only a 2 V reverse bias. We also found that the maximum photoresponsivity at 350 nm was 0.12 A/W under a 5 V reverse bias. This value corresponds to an external quantum efficiency of 34.6%.