Defect evolution in irradiated silicon detector material

A numerical model based on experimental data has been used to investigate the evolution of atomic defects in high resistivity detector material during neutron and gamma irradiation to levels expected at the CERN LHC. The complexes V2O and V3O have been identified as candidates for deep-level acceptor states which give rise to experimentally observed changes in the effective doping concentration. The phosphorus dopant is removed by production of V-P centres but at a rate lower than previously hypothesised and not fully, even after heavy irradiation. The importance of initial oxygen and carbon impurity concentrations is demonstrated in determining the radiation tolerance of the detectors. A hypothesis for the long term annealing behaviour via the thermal annealing of a trivacancy (V-3) state during neutron and heavy particle irradiation is modelled and shown to be a possible explanation of experimental observations.