Close to midgap trapping level in 60Co gamma irradiated silicon detectors

The deep level transient spectroscopy method was applied on standard and oxygenated float-zone silicon detectors exposed to high doses of Co-60-gamma irradiation. We have detected and characterized a close to midgap trapping level having an ionization energy of E-C-(0.545+/-0.005) eV and electron/hole capture cross sections of sigma(n)=(1.7+/-0.2)x10(-15) cm(2)/sigma(p)=(9+/-1)x10(-14) cm(2) respectively. This level has a strong impact on the detector performance being responsible for more than 90% of the change in the effective doping concentration. The defect is strongly oxygen related and a possible connection with the V2O complex is discussed. (C) 2002 American Institute of Physics.