Time-Dependent Impact Ionization in a Large-Size Ge Detector Made from a Crystal Grown at USD

SuperCDMS-style Ge detector made from a crystal grown at USD was operated at the University of Minnesota to observe the time-dependent impact ionization. An Am-241 movable source was used to characterize the energy spectra. The observed time-dependent impact ionization at mK temperature can be explained due to the formation of cluster dipole states. We studied the charge transport properties inside the detector at a cryogenic temperature and attempted to understand the charge collection efficiency using an empirical model. The binding energy of the charged state, A^-, was accounted for in the order of < 1meV and impact ionization scattering cross-section in the order of 10^-13 cm².