Characterisation of SiPM Photon Emission in the Dark

TL;DR

This study characterizes the photon emission of SiPMs in dark conditions, revealing spectral features, emission yields, and hotspots, to improve understanding for future large-area SiPM-based physics experiments.

Contribution

It introduces a new spectral and imaging apparatus to analyze SiPM photon emission, providing detailed emission spectra, yields, and hotspot distributions for two SiPM models.

Findings

FBK VUV-HD3 has a photon yield of ~4.04e-6 γ/e− at 12.1V over-voltage.

HPK VUV4 exhibits a higher photon yield of ~8.71e-6 γ/e− at 10.7V.

Emission spectra show interference patterns for FBK but not for HPK, indicating different surface coatings.

Abstract

In this paper, we report on the photon emission of Silicon Photomultipliers (SiPMs) from avalanche pulses generated in dark condition, with the main objective of better understanding the associated systematics for next-generation, large area, SiPM-based physics experiments. A new apparatus for spectral and imaging analysis was developed at TRIUMF and used to measure the light emitted by the two SiPMs considered as photo-sensor candidates for the nEXO neutrinoless double-beta decay experiment: one Fondazione Bruno Kessler (FBK) VUV-HD Low Field (LF) Low After Pulse (Low AP) (VUV-HD3) SiPM, and one Hamamatsu Photonics K.K. (HPK) VUV4 Multi-Pixel Photon Counter (MPPC). Spectral measurements of their light emission were taken with varying over-voltage in the wavelength range of 450--1020\,nm. For the FBK VUV-HD3, at an over-voltage of $12.1\pm1.0$\,V, we measure a secondary photon yield (number of photons ($\gamma$) emitted per charge carrier ($e^{-}$)) of $(4.04\pm0.02)\times 10^{-6}$ $\gamma/e^{-}$. The emission spectrum of the FBK VUV-HD3 contains an interference pattern consistent with thin-film interference. Additionally, emission microscopy images (EMMIs) of the FBK VUV-HD3 show a small number of highly localized regions with increased light intensity (hotspots) randomly distributed over the SiPM surface area. For the HPK VUV4 MPPC, at an over-voltage of $10.7\pm1.0$\,V, we measure a secondary photon yield of $(8.71\pm0.04)\times 10^{-6}$ $\gamma/e^{-}$. In contrast to the FBK VUV-HD3, the emission spectra of the HPK VUV4 don't show an interference pattern -- most likely due to a thinner surface coating. EMMIs of the HPK VUV4 also reveal a larger number of hotspots compared to the FBK VUV-HD3, especially in one of the corners of the device.