Deep level impurity characterization in developing Germanium detectors for detecting rare event physics*

Deep-level impurity impacts germanium detector performance in terms of charge trapping and charge carrier recombination that will eventually broaden energy resolution of germanium detectors. Deep-level impurity characterization in semiconductors is performed widely nowadays using Deep level transient spectroscopy (DLTS) technique. In this technique, the junction is reversed bias and pulse voltage is provided so that the majority charge carrier is in the depletion region. The thermal emission of holes from the deep level in the forbidden gap gives capacitance transient which is measured by the boxcar method. I will talk about the basic DLTS theory, experimental components and different peaks due to the deep level we found in high purity Germanium samples. Using this technique, the deep level traps due to doubly ionized copper and copper-Hydrogen complexes were positively identified. Several unknown traps were also observed.