Enhancement of responsivity in solar-blind beta-Ga2O3 photodiodes with a Au Schottky contact fabricated on single crystal substrates by annealing

We fabricated beta-Ga2O3 photodiodes with a Au Schottky contact on a single crystal substrate and investigated the effect of postannealing on the electrical and optical properties of the photodiodes. The ideality factor improved to near unity by annealing at temperatures above 200 degrees C; however, the reverse leakage current remained nearly unchanged. The responsivity in the wavelength region below 260 nm was enhanced dramatically by a factor of more than 10(2) after annealing at 400 degrees C resulting in maximum responsivity of 10(3) A/W, accompanied with a contrast ratio of about six orders of magnitude between the responsivities at 240 and 350 nm.