Improved solar-blind detectivity using an AlxGa1-xN heterojunction p-i-n photodiode

We report the improved detectivity of AlxGa1-xN-based solar-blind p-i-n photodiodes with high zero-bias external quantum efficiency. The zero-bias external quantum efficiency was similar to42% at 269 nm, and increased to similar to46% at a reverse bias of -5 V. In addition, the photodiodes exhibited a low dark current density of 8.2x10(-11) A/cm(2) at a reverse bias of -5 V, which resulted in a large differential resistance. The high quantum efficiency and large differential resistance combine to yield a high detectivity of D*similar to2.0x10(14) cm Hz(1/2) W-1. These results are attributed to the use of an Al0.6Ga0.4N window n region, which allows improved transmission to the absorption region, and to improved material quality. (C) 2002 American Institute of Physics.