An Ultraviolet Photon Counting Imaging System Based on a SiC SPAD Array

This letter presents a novel ultraviolet photon counting system based on a SiC SPAD array. The detector is made of 4H-SiC with a fairly low dark current in pA level and the array size is $1\times 128$ . In order to reduce the influence of dark count on image quality, this letter proposes an adaptive sampling readout circuit system, which can automatically adjust the SPAD hold-off time according to the photon density of the applications. Aiming at the nonuniform breakdown voltage of SPADs in a linear array, an adjustable bias voltage circuit is adopted to realize the accurate adjustment of pixel SPAD’s bias voltage. The ROIC is taped out in TSMC 0.18 $\mu {\mathrm{ m}}$ standard CMOS process and connected to the SPAD array by a gold bonding package. Based on the self-developed imaging system, UV photon counting imaging and deep violet- visible light fusion imaging are realized for the first time.