# Measurements of the quantum yield of silicon using Geiger-mode avalanching photodetectors

## TL;DR

This paper introduces a new method to measure the quantum yield of silicon using specialized photodetectors, which could improve the sensitivity of experiments in dark matter detection and UV photodetector performance.

## Contribution

A novel experimental method for calculating quantum yield in silicon using SiPMs and DC current–voltage measurements.

## Key findings

- Quantum yield values measured are lower than previously reported, impacting dark matter detection experiments.
- The method was validated using Hamamatsu VUV4 and FBK VUV-HD3 devices with consistent results across temperatures.
- A new DC current–voltage measurement technique corroborates the quantum yield results.

## Abstract

Accurate characterization of quantum yield is crucial to the reconstruction of energy depositions in silicon at the eV scale. This work presents a new method for experimentally calculating quantum yield using vacuum UV-sensitive silicon photomultipliers (SiPMs), which can be used to determine the probabilities that a UV photon absorbed in a silicon crystal will produce one, two, or three electron–hole pairs. Results are presented which fully constrain the distribution at photon energies up to 7.75 eV. This method works by exploiting the saturation of photon detection efficiency which occurs when these devices are biased sufficiently high above their avalanche breakdown voltage. The measured quantum yield values are lower than those that have been previously reported by experimental data and modelling – this is expected to impact the sensitivity of experiments searching for light dark matter through direct detection in semiconductors, and should also be taken into account when characterizing the performance of UV photodetectors with high quantum efficiency. Measurements have been taken using a Hamamatsu VUV4 and an FBK VUV-HD3 device, showing good agreements between devices, and at a range of temperatures from 163–233 K. The validity of the method is assessed using supplementary measurements of absolute photon detection efficiency, and an additional novel method of measuring average quantum yield using DC current–voltage measurements of SiPMs is presented and used for corroboration.