Dark Count Rate Dependence on Bias Voltage During Gate-OFF in InGaAs/InP Single-Photon Avalanche Diodes

We characterized the dependence of the dark count rate (DCR) of InGaAs/InP single-photon avalanche diodes on the bias voltage during the OFF time when operated in gated mode. When the OFF bias voltage is too low, there is a strong increment of DCR particularly at temperatures >225 K. Measurements of DCR at different gate periods show that this effect is not related to afterpulsing, but to primary carrier generation. We infer that it is due to trapping at the heterobarrier and subsequent release of holes thermally generated in the InGaAs layer.