Abstract
In this paper, we report on the photon emission of Silicon Photomultipliers (SiPMs) from avalanche pulses generated in dark conditions, 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 emissions were taken with varying over-voltage in the wavelength range of 450–1020 nm. For the FBK VUV-HD3, at an over-voltage of V, we measured a secondary photon yield (number of photons () emitted per charge carrier ()) of . 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 V, we measured a secondary photon yield of . In contrast to the FBK VUV-HD3, the emission spectra of the HPK VUV4 did not show an interference pattern—likely due to a thinner surface coating. The EMMIs of the HPK VUV4 also revealed a larger number of hotspots compared to the FBK VUV-HD3, especially in one of the corners of the device. The photon yield reported in this paper may be limited if compared with the one reported in previous studies due to the measurement wavelength range, which is only up to 1020 nm.
Highlights
Since the number of photons emitted per charge carrier is rather low, and this paper focuses on Silicon photo-multipliers (SiPM) photon emission driven by avalanche pulses generated in dark conditions, the high over-voltage is needed to generate a sufficiently large number of carriers in the SiPMs such that the light emitted by the SiPM was resulting in a reasonable signal to noise at the Princeton Instruments (PI) CCD camera
Where (i) Rk, with k = {1, 2, 3} are the regions highlighted in Figure 5 for the Hamamatsu Photonics K.K. (HPK) VUV4 and for the Fondazione Bruno Kessler (FBK) Vacuum Ultra-Violet (VUV)-HD3, and (ii) PiM,j are the number of photons counted in the i, jth pixel recorded by the CCD camera for an image at magnification M
Paired with careful measurements of the SiPM Photon Detection Efficiency (PDE) [32] in the IR and NIR, this figure contains enough information to estimate the contribution of the SiPM secondary photon emission on the total background rate for any large-area SiPM-based detectors; this is crucial for experiments, such as nEXO and DarkSide-20k, where the SiPMs will likely be arranged facing each other
Summary
An unfortunate by-product of the avalanche generation process is the emission of secondary photons [8], which, in some works on SiPM characterisation, are referred to as cross-talk photons [9,10]. Even if an exhaustive list of production mechanisms is not known conclusively at present, avalanche emission in silicon appears to be due to a combination of (i) indirect interband transitions, (ii) intraband Bremsstrahlung processes and (iii) direct interband transitions [13,14,15]. Each of these mechanisms are responsible for light emission in different spectral regions, i.e., at certain wavelengths.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
