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-mum-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
k
= 0.1. Detection of several tens of femtowatts of ultraviolet light is reported.