Determination of impact ionization parameters for low gain avalanche detectors produced by HPK

Abstract A set of unirradiated Low Gain Avalanche Detectors from Hamamatsu Photonics from the HGTD prototype 2 run for the upgrade of experiments at the High Luminosity Large Hadron Collider were used to determine the impact ionization parameters for silicon, particularly in the electric field range of ∼30 V/μm which is of interest for LGADs. The parameters' dependence on temperature was also determined. Their validity on irradiated sensors up to 2.5·1015 cm-2 was also tested and found to be acceptable at low biases but further work should be done to determine the dependence on fluence.