Charge collection efficiency recovery in heavily irradiated silicon detectors operated at cryogenic temperatures

The charge collection efficiency (CCE) of high resistivity silicon detectors, previously neutron irradiated up to 2/spl times/10/sup 15/ n/cm/sup 2/, was measured at different cryogenic temperatures and different bias voltages. In order to study reverse annealing (RA) effects, a few samples were heated to 80/spl deg/C and kept at room temperature for several months after irradiation. For comparison other samples (NRA) where kept at -10 C after irradiation. The RA and NRA samples, measured at 250 V forward and reverse bias voltage, present a common temperature threshold at 150 K. Below 120 K the CCE is constant and ranges between 55% and 65% for the RA and NRA sample respectively. Similar CCE was measured for a device processed with low resistivity contacts (OHMIC), opening the prospect for a consistent reduction of the cost of large area particle tracking.