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 mu W/cm(2) illumination. Dark current density as low as 2.6 x 10(-11) A/cm(2) 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 x 10(14) cm.Hz(1/2)/W at 300 K.