Fig. 1. (A) Schematic of general structure of a SiPM microcell; (B) working principle of the SiPM; and (C) pulse shape corresponding to a single detected optical photon.

Fig. 2. (A) The SiPM is an intrinsically digital technology. When a particle (here a γ-ray as an example) is detected in the scintillator, scintillation optical photons are produced. They are detected in the microcells composing the SiPM. (B) Each detected optical photon generates a signal. The time sequence of all signals generates a temporal-only digital signal, which can be analyzed to extract energy, interaction time, and depth of interaction information. (C)–(E) The time sequence of the signals for each microcell generates a spatiotemporal series of digital signals, which can be modeled to extract with higher precision the information about the interaction of the primary particle.

Fig. 3. Characterization of CMOS SiPMs. (A) DCR of SPADs and SiPMs obtained in standard CMOS technology nodes; (B) PDE; and (C) SPTR versus number of microcells of available CMOS SiPMs. The shaded area in (A) and (B) is covered by customized commercial technologies and represents the benchmark target of CMOS SiPMs.

Fig. 4. CMOS SiPM developed at a 350 nm technology and currently commercialized also in arrays (TN and TP series, JOINBON).

Fig. 5. Prototype of MT-SiPM; photo of the chip and example of detection map of a 420 nm LED photon flux with 1 kHz rate.