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

This paper 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 1×128. In order to reduce the influence of dark count on image quality, this paper 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 0.18um 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.