Sources of Internal Crosstalk in Silicon Photomultipliers

Silicon photomultipliers (SiPMs) have been widely adopted for photon detection in next-generation dark matter and neutrino detection experiments. Internal crosstalk (iCT), resulting from secondary photons produced during avalanche multiplication,is a significant noise mechanism in SiPMs.This work presents experimental data for trends in iCT probability with temperature and overvoltage for two different SiPM devices, and demonstrates a novel method for determining the region within the SiPM in which the primary carriers for crosstalk avalanches originate. This is done by using measurements of avalanche triggering probabilities for different charge carrier types to identify the device regions in which crosstalk avalanches are produced. This is possible because secondary photons absorbed in n-doped regions will produce hole-triggered avalanches, and those absorbed in p-doped regions will produce electron-triggered avalanches. The relative probabilities of different optical transmission paths for secondary photons can therefore be evaluated, and the effectiveness of existing crosstalk mitigation methods for each optical pathway can be assessed. We identify optical reflections from the device surface as a significant source of crosstalk, likely to dominate in devices with effective crosstalk mitigation in bulk.