Design and performance study of actively holding-off GHz-gated InGaAs/InP SPADs

High-speed periodic gating of InGaAs/InP single-photon avalanche diodes (SPADs) has allowed these detectors to operate at count rates above 108 per second with low afterpulsing. However, a drawback of high-speed periodic gating is that bias gates are applied continuously, regardless of whether an avalanche has occurred or not. This is disadvantageous because gates immediately following an avalanche have elevated afterpulse probabilities, and the additional charge from these secondary events contributes to the overall afterpulse probability. We investigate this phenomenon in a proof-of-principle experiment in which the series of bias gates is briefly interrupted after an avalanche, and we measure the resulting impact on the afterpulse probability. We observe a significant reduction in afterpulsing when such a bias-gate hold-off is applied to an InGaAs/InP SPAD gated at 1.25 GHz; when one bias gate is omitted after an avalanche the per-gate afterpulse probability is reduced by more than 40 %. These results indicate that afterpulsing noise at high count rates can be further reduced in high-speed-gated SPADs.