Solar-blind AlGaN-based p-i-n photodiodes with low dark current and high detectivity

We report solar-blind AlxGa1-xN-based heterojunction p-i-n photodiodes with low dark current and high detectivity. After the p+ GaN cap layer was recess etched, measured dark current was below 3 fA for reverse bias values up to 6 V The device responsivity increased with reverse bias and reached 0.11 A/W at 261 nm under 10-V reverse bias. The detectors exhibited a cutoff around 283 nm, and a visible rejection of four orders of magnitude at zero bias. Low dark current values led to a high differential resistance of 9.52 x 10(15) Omega. The thermally limited detectivity of the devices was calculated as 4.9 x 10(14) cm (.) Hz(1/2)W(-1).