High-speed solar-blind photodetectors with indium-tin-oxide Schottky contacts

We report AlGaN/GaN-based high-speed solar-blind photodetectors with indium-tin-oxide Schottky contacts. Current–voltage, spectral responsivity, and high-frequency response characterizations were performed on the fabricated Schottky photodiodes. Low dark currents of $\text{<1\hspace{0.17em}}\mathrm{pA}$ at 20 V reverse bias and breakdown voltages larger than 40 V were obtained. A maximum responsivity of 44 mA/W at 263 nm was measured, corresponding to an external quantum efficiency of 21%. True solar-blind detection was ensured with a cutoff wavelength of 274 nm. Time-based high-frequency measurements at 267 nm resulted in pulse responses with rise times and pulse-widths as short as 13 and 190 ps, respectively. The corresponding 3-dB bandwidth was calculated as 1.10 GHz.