A Search for Deep Trap Levels in Ge(Li) Detectors

We have attempted to measure the level of deep electron trapping centres in Ge(Li) detectors by observing the variation of pulse amplitude with temperature over a wide temperature range. The mean time TD for the re-emission of a trapped carrier from a given level decreases exponentially with increasing temperature; as TD becomes shorter than the amplifier time constants, pulse amplitude should show an increase over a narrow temperature interval. No such transition was observed between 80 and 160 K. We conclude that the main electron trap is deeper than 0.175 eV.