Characterization of the First FBK High-Density Cell Silicon Photomultiplier Technology

In this paper, we present the results of the characterization of the first high-density (HD) cell silicon photomultipliers produced at FBK. The most advanced prototype manufactured with this technology has a cell size of 15 × 15 μm² featuring a nominal fill factor of 48%. To reach this high area coverage, we developed a new border structure to confine the high electric-field region of each single-photon avalanche diode. The measured detection efficiency approaches 30% in the green part of the light spectrum and it is above 20% from 400 to 650 nm. At these efficiency values, the correlated noise is very low, giving an excess charge factor below 1.1. We coupled a 2 × 2 × 10- mm³ LYSO scintillator crystal to a 2.2 × 2.2- mm² silicon photomultiplier, obtaining very promising results for PET application: energy resolution of less than 11% full-width at half maximum (FWHM) with negligible loss of linearity and coincidence resolving time of 200-ps FWHM at 20°C.