STUDY OF BULK DAMAGE IN HIGH-RESISTIVITY SILICON DETECTORS IRRADIATEDBY HIGH-DOSE OF CO-60 GAMMA-RADIATION

Displacement damage (or bulk damage) induced by high dose (>200 Mrad) gamma-radiation in high resistivity (6-10 k Omega-cm) silicon detector s has been studied. It has been found that detector bulk leakage curre nt increases with gamma dose at a rate of 3.3x10(-7) A/cm(3)/Mrad. Thi s damage rate of bulk leakage current originates from the introduction of generation centers and at a dose of 210 Mrad of gamma-radiation is comparable to that induced by 1x10(12) n/cm(2) of neutron radiation. Nearly 100% donor removal and/or compensation was found in detectors i rradiated to 215 Mrad. Space charge sign inversion (SCSI) was observed in detectors irradiated to greater than or equal to 215 Mrad using tr ansient 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 elevat ed temperature treatment for detectors irradiated to 215 Mrad. A small amount of reverse annealing (10 to 15%) has been observed during the room temperature storage period of about 11 months for detectors irrad iated to 500 Mrad.