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In the last years. custom-technology single-photon avalanche diodes (SPADs) have demonstrated remarkable performance, thanks to the fine engineering process performed on the electric field profile. However, the integration of custom SPADs in detector arrays often conflicts with the low-threshold current sensing that is mandatory to extract the timing information. A new custom-technology SPAD is introduced, that exploits an extra epitaxial layer in order to reduce the capacitive coupling between the anode and the chip substrate. The new detector shows a state-of-the-art timing jitter of 34 ps full width at half maximum and a weak dependence on the detection threshold, even when the substrate is kept at a fixed voltage, as required by the implementation of multichannel photon timing systems.

Excellent performance of custom technology SPAD detectors have been widely demonstrated in recent years. Low-jitter timing measurements with these detectors require front end electronics able to sense the avalanche current at a very low level when the multiplication process is still confined in a very small area around the photon absorption point. Best in class results (35 ps full width at half maximum) have been obtained with discrete circuits not suitable to be used in densely integrated systems of SPAD arrays required by modern demanding applications. A new fully integrated front end able to read out the avalanche current with a timing jitter as low as 32 ps and suitable to be exploited with SPAD arrays is presented.