GHz-gated silicon single-photon avalanche photodiode at high efficiency and high speed

Silicon single-photon avalanche diodes (SPADs) are essential for low-light detection in applications ranging from quantum communication to LiDAR. Thick-junction Si SPADs offer higher quantum efficiency than thin-junction designs but typically suffer from limited count rates and timing performance. Here, we demonstrate a commercially available thick-junction Si SPAD operated in sinusoidally gated Geiger mode at 1 GHz and 850 nm. By combining high-amplitude sinusoidal gating (38 V peak-to-peak) with cascaded low-pass filtering, we efficiently suppress capacitive noise and rapidly quench avalanche events, reducing afterpulsing and self-heating. The device achieves a photon detection efficiency of 63.1% with a quantum efficiency of 66.2% (corresponding to an avalanche probability of ∼95%), while maintaining an exceptionally low afterpulse probability of only 3.8% and an ultralow timing jitter of ∼84 ps full width at half maximum. Under pulsed illumination, the maximum count rate reaches 500 M counts/s, a substantial improvement over previous Si SPADs. These results highlight the potential of GHz-gated Si SPADs for high-speed optical communication, ranging, deep-space sensing, and advanced quantum technologies.