A Passive-Quenching Active-Recharge Analog Silicon Photomultiplier

In this paper, we present a novel analog silicon photomultiplier (SiPM) structure, characterized by the passive-quenching active-recharge operation of the microcells (PQAR). The structure is obtained by including a MOSFET transistor close to each microcell. The transistor is built without any changes to the standard SiPM micro-fabrication process, and it does not significantly reduce the fill factor of the device. We operated this detector in a periodic pulsed reset mode. The advantages of this approach include a reduction in the effective dark count rate, strong suppression of afterpulsing, very short pulse duration, and lower fabrication cost. In this paper, we provide a description and the results of the preliminary characterization of the first 1 × 1-mm² prototype of the structure, with 50 × 50-μm² cells, fabricated at Fondazione Bruno Kessler (FBK). The measured duration of the single-cell response is only 3.4 ns FWHM. Employing a pulsed light source, we were able to measure a very sharp pulse-charge spectrum with a good photon counting capability of up to 40 detected photons and more because of the absence of after pulses.