Gamma-Ray Irradiation Effects on the Rise Time of Au-Si Nuclear Detectors

The carrier collection time distributions of 60-Co gamma-ray irradiated and non-irradiated detectors as a function of bias voltage have been obtained by measuring the output pulse rise time of the detectors counting 241-Am alpha-particles. The pulse rise time of the detector with 5×l07R is distinctly slow as compared with that of the non-irradiated detector, and has the broad distribution and the slow rise time tailing distribution even at high bias voltage. This is the effect of the defects induced in silicon with the gamma-ray irradiation. From the deep-level transient spectroscopy (DLTS) spectra of the irradiated detector, an energy level of these defects is determined to be at 0.46±0.01eV below the conduction band, and is similar to the level of the phosphorus-vacancy state induced in silicon by charged particle irradiation.