Fast Free-Running Circuits for 4H-SiC Avalanche Photodiodes

4H-SiC APDs show excellent characteristics in ultraviolet detection. Requirements have been put forward for quenching circuits in high-performance single photon detection applications. Here, a fast free-running circuit is proposed with passive quenching and active resetting for the 4H-SiC APD, which achieves a 23.8 ns dead time. The detection performance of the 4H-SiC APD under different dead times were studied. The photon detection efficiency and detectable distance increase with the decreasing dead time, remaining the highest at the shortest dead time. A dead time of 23.8 ns, detectable distance of 16.8 m and photon detection efficiency of 15.5% at 275 nm are achieved.