High detection sensitivity of ultraviolet 4H-SiC avalanche photodiodes

We report 4H-SiC p-i-n avalanche photodiodes (APDs) with very low dark current. When biased for a photocurrent gain M of 1000 a 100-mu m-diameter device exhibits dark current of 5 pA (63 nA/cm(2))corresponding to primary multiplied dark current of 5 fA (63 pA/cm(2)). The peak responsivity at unity gain is 93 mA/W (external quantum efficiency = 41%) at lambda =280 nm. The excess noise factor corresponds to kappa = 0.1. Detection of several tens of femtowatts of ultraviolet light is reported.