Low-Dark-Current High-Performance AlGaN Solar-Blind p–i–n Photodiodes

We report on the fabrication and characterization of high-performance AlGaN solar-blind p–i–n photodiodes grown on AlN/sapphire templates by metal organic chemical vapor deposition. The realized devices demonstrate a sharp spectral cutoff with a drop of four orders of magnitude from 260 to 310 nm under the 1 µW/cm2 illumination. Dark current density as low as 2.6×10-11 A/cm2 at -5 V bias has been measured. The zero bias external quantum efficiency peaks at 258 nm with a value of 30%. The upper-bound detectivity limited by Johnson noise is calculated to be 7.1×1014 cmHz1/2/W at 300 K.