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The deep level transient spectroscopy method was applied on standard and oxygenated float-zone silicon detectors exposed to high doses of Co60–gamma irradiation. We have detected and characterized a close to midgap trapping level having an ionization energy of EC−(0.545±0.005) eV and electron/hole capture cross sections of σn=(1.7±0.2)×10−15 cm2/σp=(9±1)×10−14 cm2 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.

Radiation-induced defects in silicon diodes were investigated after exposure to high doses of Co60-gamma irradiation using the thermally stimulated current method. We have found that, for high irradiation doses, a second-order defect can be detected. This defect is largely suppressed in oxygen-enriched material while it is the main cause for the space charge sign inversion effect observed in standard float-zone material.

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