High-Speed Solar-Blind AlGaN Schottky Photodiodes

We report high-speed solar-blind AlGaN-based Schottky photodiodes. AlGaN/GaN heterostructure device layers were grown on sapphire substrate. The devices were fabricated on AlGaN/GaN heterostructuresusing a microwave compatible fabrication process. Schottky photodiodes with Au and indium-tin-oxide (ITO) Schottky contacts were fabricated. Current-voltage, spectral responsivity, and high-speed measurements were performed. Both Schottky samples exhibited very low sub-pA dark currents at high reverse bias. A bias dependent spectral responsivity was observed with a peak responsivity of 89 mA/W at 267 nm, and 44 mA/W at 263 nm for Au and ITO-Schottky devices respectively. Time-based high-frequency measurements at 267 nm resulted in pulse responses with rise times and pulse-widths as short as 13 ps and 74 ps respectively. The fastest solar-blind detector had a record 3-dB bandwidth of 1.10 GHz.