Impact of Resistance on the Performance of Ultraviolet 4H-SiC Avalanche Photodiodes

In this work, ultraviolet (UV) 4H-SiC avalanche photodiodes (APDs) with a diameter of 150 μm were fabricated and investigated. The impact of resistance on the performance of 4H-SiC APDs was analyzed both in linear and Geiger modes. The optical response time of the fabricated APD devices in linear mode was measured with various load resistances, whereas the single photon counting performance in Geiger mode was carried out based on the passive-quenching circuit with different quenching resistances. The results show that the response time and the single-photon counting performance are strongly dependent on the series resistances. The response time (i.e., rising time and falling time) in the linear mode increases almost linearly with the load resistance increasing. In the Geiger mode, the photon count rate (PCR) decreases with the increasing quenching resistance. However, at some reverse bias voltages, the ratio of single photon detection efficiency (SPDE) to dark count rate (DCR) is positively correlated to the quenching resistance. Therefore, in order to obtain the optimal performance of 4H-SiC APDs, the resistance in the circuit must be carefully adjusted for practical usage. The results in this work will be very useful and can provide a reference for researchers in the fields of 4H-SiC APD UV detectors.