High detectivity GaN metal–semiconductor–metal UV photodetectors with transparent tungsten electrodes

Abstract

GaN metal–semiconductor–metal (MSM) ultraviolet photodetectors with transparent tungsten (W) electrodes were fabricated and characterized. It was found that the 10 nm thick W film deposited with a 250 W RF power could provide a reasonably high transmittance of 68.3% at 360 nm, a low resistivity of 1.5 × 10−3 Ω cm and an effective Schottky barrier height of 0.777 eV on u-GaN. We also achieved a peak responsivity of 0.15 A W−1 and a quantum efficiency of 51.8% at 360 nm from the GaN MSM UV photodetector with W electrodes. With a 2 V applied bias, it was found that the minimum noise equivalent power (NEP) and the maximum D* of our detector were 1.745 × 10−10 W and 7.245 × 109 cm Hz0.5 W−1, respectively.