Characterization of the large-size NDL EQR20 silicon photomultipliers

Abstract

Unlike most commercially available silicon photomultipliers (SiPMs), EQR20 SiPMs produced by the Novel Device Laboratory (NDL) avoid using individual resistors to quench the avalanche multiplication of the microcells. Instead, bulk resistance of the epitaxial silicon layer is used, and the signal is directly collected at a common anode plane. This allows for the fabrication of SiPMs as large as 6.24 x 6.24 mm^2 while keeping the recovery time below τ = 25 ns. These devices can be composed of microcells with 20 micrometer pitch while reaching PDE above 50% and 10^6 gain at 5 V overvoltage. On the other hand, a crosstalk level from 20% to 40% is observed for overvoltages from 3 V to 5 V. Moreover, significant pulse shape distortion is observed for pulses above ~100 pC, corresponding to microcell occupancy of a few percent. This work provides an independent determination of the performance parameters of the EQR20 11-6060D-S SiPMs. Influence of the pulse shape distortion is discussed from the perspective of the applicability of these devices to the scintillator-based forward hadron calorimeter (FoCal-H) of the ALICE apparatus at CERN.