GaN ultraviolet photodetectors with transparent titanium tungsten and tungsten electrodes

GaN metal-semiconductor-metal (MSM) ultraviolet photodetectors with titanium tungsten (TiW) and tungsten (W) transparent electrodes were fabricated and characterized. It was found that the 10-nm-thick TiW and W films could provide a reasonably high transmittance of 78 and 65.4% at 300 nm, a low resistivity of 1.7 and 1.5 X 10(-3) Omega cm, and an effective Schottky barrier height of 0.773 and 0.777 eV on u-GaN, respectively. We also achieved a peak responsivity of 0.192 and 0.15 A/W, a quantum efficiency of 66.4 and 51.8% from the GaN UV MSM photodetector with TiW and W electrodes, respectively. With a 3 V applied bias, the noise equivalent power of photodetectors with TiW and W electrodes were estimated to be 1.98 X 10(-10) W and 3.36 X 10(-10) cm Hz(0.5) W-1, corresponding to the normalized detectivity (D-*) of 6.36 and 3.82 X 10(9) cm Hz(0.5) W-1, respectively. (c) 2005 The Electrochemical Society. All rights reserved.