A 0.93 g $1\times 1\times 0.4{\mathrm{cm}}^3$ SuperCDMS silicon HVeV detector operated at 30 mK was illuminated by 1.91 eV photons using a room temperature pulsed laser coupled to the cryostat via fiber optic. The detector’s response under a variety of specific operating conditions was used to study the detector leakage current, charge trapping, and impact ionization in the high-purity Si substrate. The measured probabilities for a charge carrier in the detector to undergo charge trapping ($0.713\pm 0.093\%$) or cause impact ionization ($1.576\pm 0.110\%$) were found to be nearly independent of bias polarity and charge-carrier type (electron or hole) for substrate biases of $\pm 140\mathrm{V}$.

• Received 9 December 2019
• Accepted 24 January 2020

DOI:https://doi.org/10.1103/PhysRevD.101.031101