# Free-running 4H-SiC single-photon detector with ultralow afterpulse probability at 266 nm

## TL;DR

This paper presents a novel free-running 4H-SiC single-photon detector operating at 266 nm with ultralow afterpulse probability, high photon detection efficiency, and potential for practical ultraviolet photon-counting applications.

## Contribution

The authors design and fabricate a 4H-SiC SPAD with a beveled mesa structure and develop a readout circuit that significantly suppresses afterpulsing, advancing UV single-photon detection technology.

## Key findings

- Achieved 10.3% PDE at 266 nm
- Reduced afterpulse probability to 0.3%
- Demonstrated practical performance with 133 kcps dark count rate

## Abstract

Ultraviolet single-photon detector (UVSPD) provides a key tool for the applications requiring ultraweak light detection in the wavelength band. Here, we report a 4H-SiC single-photon avalanche diode (SPAD) based free-running UVSPD with ultralow afterpulse probability. We design and fabricate the 4H-SiC SPAD with a beveled mesa structure, which exhibits the characteristic of ultralow dark current. We further develop a readout circuit of passive quenching and active reset with tunable hold-off time setting to considerably suppress the afterpulsing effect. The nonuniformity of photon detection efficiency (PDE) across the SPAD active area with a diameter of $\sim$ 180 $\mu$m is investigated for performance optimization. The compact UVSPD is then characterized, exhibiting a typical performance of 10.3% PDE, 133 kcps dark count rate and 0.3% afterpulse probability at 266 nm. Such performance indicates that the compact UVSPD could be used for practical ultraviolet photon-counting applications