Study of bulk damage in high resistivity silicon detectors irradiated by high dose of 60Co γ-radiation

Displacement damage (or bulk damage) induced by high dose (>200 Mrad) of γ-radiation in high resistivity (6-10 kΩ-cm) silicon detectors has been studied. It has been found that detector bulk leakage current increases with γ dose at a rate of 3.3×10 ^-7 A/cm³/Mrad. This damage rate of bulk leakage current originates from the introduction of generation centres and at a dose of 210 Mrad of γ-radiation is comparable to that induced by 1×10¹² n/cm² of neutron radiation. Significant donor removal, about 100%, was found in detectors irradiated to 215 Mrad. Space charge sign inversion (SCSI) (or more conventional term “type inversion”, which is a term for neutral material and should be considered as equivalent in terms of the net effective concentration) was observed in detectors irradiated to ⩾215 Mrad using the transient current technique (TCT). As many as six deep levels have been observed by current deep level transient spectroscopy (I-DLTS). There was insignificant annealing and no reverse annealing even after elevated temperature treatment for detectors irradiated to 215 Mrad. A small amount of reverse annealing (10 to 15%) during the room temperature storage period of about 11 months for detectors irradiated to 500 Mrad has been observed