Solar-blind AlGaN-based Schottky photodiodes with high detectivity and low noise

We report on the design, fabrication and characterization of solar-blind Schottky photodiodes with high detectivity and low noise. The devices were fabricated on n-/n+ AlGaN/GaN hetero-structures using a microwave compatible fabrication process. Using Al0.38Ga0.62N absorption layer, true solar-blind operation with a cutoff wavelength of ∼274 nm was achieved. The solar-blind detectors exhibited < 400 fA dark current in the 0-25 V reverse bias regime, and a maximum responsivity of 89 mA/W around 267 nm. The photovoltaic detectivity of the devices were in excess of 2.6×1012 cmHz1/2/W, and the detector noise was 1/f limited with a noise power density less than 3×10-29 A2/Hz at 10 KHz