Time-dependent polarization of CdTe gamma-ray detectors

Abstract A decrease in the counting rate and charge collection efficiency of p-type CdTe gamma-ray detectors, starting from the time of first application of the electric field, has been observed. Momentary removal of the bias returns the detector to its initial state. The behavior can be understood in terms of deep acceptors which detrap holes and decrease the thickness of the space charge region. Non-polarizing detectors can be made by using either high work function contacts with appropriate surface preparation or by periodic removal of the bias.