5×5 SPAD matrices for the study of the trade-offs between fill factor, dark count rate and crosstalk in the design of CMOS image sensors

CMOS Single Photon Avalanche Diodes (SPADs) are a dedicated type of photodetectors that are attracting increasing interest. Crosstalk and fill factor are magnitudes that become important when dealing with arrays of SPADs. There are trade-offs that involve these two magnitudes and dark count rate (DCR) which are of great interest for the implementation of image sensors. A set of 5×5 matrices of SPADs with different sizes and shapes is designed to study the relationships between FF, crosstalk and DCR, and conceive an accurate behavioural model of SPAD arrays. The testchip is fully operative and preliminary experimental results are presented.