Bulk damage effects in standard and oxygen-enriched silicon detectors induced by 60Co-gamma radiation

The influence of oxygen in silicon on bulk damage effects induced by 60Co-gamma irradiation has been studied in a dose range between 0.2 and 900 Mrad. The detector processing and oxygen enrichment were carried out in a common project by the Institute of Micro-sensors CiS using n-type high-resistivity FZ silicon (3–6 kΩ cm) with 〈1 1 1〉 and 〈1 0 0〉 orientation. Different oxygen concentrations were achieved by diffusion at 1150°C for 24, 48 and 72 h. This report on bulk damage effects is focussed on the observed changes in the reverse current, the effective space charge density Neff extracted from C/V measurements and investigations using the transient current technique. A substantial improvement of radiation hardness concerning the development of the macroscopic properties was found for detectors manufactured on oxygenated material compared to standard material. It will be demonstrated that the change of the effective space charge density as well as the increase of the reverse current can be attributed to the creation of two deep acceptor levels and a shallow donor level.