Source 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, resulting from secondary photons produced during charge avalanches, is a significant noise mechanism in SiPMs and is likely to impact the performance of physics detectors. This work presents experimental data for trends in crosstalk probability with temperature and overvoltage for two different SiPM devices, and demonstrates a novel method for identifying the source mechanisms of crosstalk avalanches. 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 crosstalk photons absorbed in n-doped regions will produce hole-triggered avalanches, and those absorbed in p-doped regions will produce electron-triggered avalanches. Thus crosstalk probability can be related to device structure to assess the effectiveness of existing crosstalk mitigation methods. 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. Lastly, a diagnostic technique is presented to identify and reduce crosstalk in novel SiPM structures.