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We report on the design, fabrication and characterization of a back-illuminated voltage bias selectable dual-band AlGaN UV photodetector. The photodetector can separate UVA and W-B band radiation by bias switching a two terminal n-p-n homojunction structure that is fabricated in the same pixel. When a forward bias is applied between the top and bottom electrodes, the detector can sense UV-A and reject W-B band radiation. Alternatively, under reverse bias, the photodetector can sense UV-B and reject UV-A band radiation.

Using conventional photolithography, Al 0.35 Ga 0.65 N pin diodes have been fabricated that exhibit extremely low reverse bias leakage currents. Macroscopic I-V measurements from a statistical population of 64, 120 μm diameter, circular diodes gives a mean leakage current of 0.96 fA with a standard deviation of 0.90 fA at -0.5 V bias.

Pt/n-type GaN Schottky photodiodes with large active areas which exhibit low leakage currents are fabricated. Reverse bias leakage currents of 2.7 nA for a 1 cm2 diode and 14 pA for a 0.25 cm2 diode both at −0.5 V bias are reported. External quantum efficiency measurements between the spectral range 50 to 500 nm gave a peak responsivity of 77.5 mA/W at 320 nm for a 0.25 cm2 diode, corresponding to a spectral detectivity, D*=1.5×1014 cmHz1/2W−1.