Cryogenic investigations and modelling of inter-defect charge exchange in silicon particle detectors

Abstract Silicon detectors in particle physics experiments at the CERN Large Hadron Collider (LHC) will be exposed to high levels of damaging radiation. The resulting changes in detector doping concentration ( N eff ) have been identified as the principal obstacle to long-term operation in the LHC environment. We have previously proposed a model whereby the transfer of charge between closely spaced defects in the terminal clusters formed during heavy particle irradiation is responsible for a significant fraction of these changes in N eff . The defects involved, the divacancy (V 2 ) and two unidentified intrinsic defects known as E70 and E170, are postulated to exchange charge via a manifestly non-Shockley–Read–Hall mechanism. Although the model has been remarkably successful in describing experimental measurements at room temperature, direct observations of the charge exchange process have not been forthcoming, not least because of the complexity of the spectroscopic techniques required. We present a comparison between cryogenic measurements of N eff and the predictions of the model in order to test further the validity of our work to date.