NUV-sensitive Deep-junction (NUV-DJ) SiPMs, a new technology optimized for fast timing applications

In recent years, Fondazione Bruno Kessler (FBK, Trento, Italy) has developed several Silicon Photomultiplier (SiPM) technologies, particularly for applications such as time of flight-positron emission tomography (ToF-PET) where fast timing is crucial. This work presents the latest development at FBK, the Near-Ultraviolet, Deep-junction (NUV-DJ) SiPM technology, providing improved Photon Detection Efficiency (PDE) and Single Photon Time Resolution (SPTR) with respect to the state-of-the-art SiPMs. The NUV-DJ microcell has a 40 μm pitch and features a modified design with the high-electric field region placed deeper inside the epitaxial layer, enabling an increased avalanche triggering probability even with longer-wavelength photons. The PDE showed outstanding values of 70% at 420 nm (with a nominal microcell fill factor of 80.8%). At 65% PDE, DCR of 80 kcps/mm2 and Optical Crosstalk probability below 2% were measured. Using a high-frequency readout, SPTR of 36 ps FWHM and of 65 ps FWHM were measured on 1x1 mm² and 4x4 mm² SiPMs, respectively. Coincidence Time Resolution (CTR) of less than 100 ps FWHM in the readout of 2.76x2.76x18 mm³ LYSO:Ce crystals was achieved with a high frequency readout, while a CTR of 115 ps FWHM was measured using standard readout electronics. These findings represent cutting-edge advances in timing and PDE performance and are very promising for TOF-PET and high-energy physics applications employing LYSO, LSO, BGO, and LaBr3 crystals, in scenarios where a high PDE in the NUV range combined with excellent timing is needed.