GaN metal-semiconductor-metal ultraviolet photodetectors with transparent indium-tin-oxide Schottky contacts

Indium-tin-oxide (ITO) layers were deposited onto n-GaN films and/or glass substrates by electron-beam evaporation. With proper annealing, we found that we could improve the optical properties of the ITO layers and achieve a maximum transmittance of 98% at 360 mm, GaN-based metal-semiconductor-metal (MSM) photodetectors with ITO transparent contacts were also fabricated. A maximum 0.12-A photocurrent with a photo current to dark current contrast higher than five orders of magnitude during ultraviolet irradiation were obtained for a photodetector annealed at 600 degreesC. We also found that the maximum photo responsivity at 345 nm is 7.2 and 0.9 A/W when the detector is biased at 5 and 0.5 V, respectively.