Measurements and modelling of secondary photon emission from SPADs and SiPMs

This work presents experimental and modelling results for the secondary emission of photons in Single Photon Avalanche Diodes (SPADs) and Silicon Photomultipliers (SiPMs). Recombination of high-energy charge carriers during an avalanche can themselves produce photons, which may trigger secondary avalanches in other pixels of an SiPM or in other devices within a larger detector system. Accurate characterization of such ‘crosstalk’ noise mechanisms aids in precise photon counting using SiPMs and is essential for the design of detectors containing many such devices. The Microscope for the Injection and Emission of Light (MIEL) setup at TRIUMF has been used to measure the spectrum and number of photons emitted by laser-stimulated avalanches in various SiPMs, including conventional analogue devices and a ‘digital’ SiPM. A digital device allows SPAD pixels to be individually controlled, meaning that emission from a single SPAD can be measured with surrounding pixels deactivated in order to minimize systematic error. Measurement results will be presented alongside modelling of photon transport through an SiPM structure, relating the number of photons emitted from a device to the number produced by an avalanche within the silicon crystal. This permits a consideration of the recombination mechanisms which produce secondary photons, enabling generalization to the emission characteristics of a wide range of SPAD and SiPM structures and the optimized design of detectors with minimal crosstalk noise.