Charge transport in non-irradiated and irradiated silicon detectors

A model describing the transport of the charge carriers generated in n-type silicon detectors by ionizing particles is presented. In order to reproduce the experimental current pulse responses induced by α and β particles in non-irradiated and irradiated detectors up to fluences (Φ) much beyond the n to p-type inversion, an n-type region 15 μm deep is introduced on the p+ side of the diode. This model also gives mobilities which decrease linearly up to fluences of around 5×1013 particles/cm2 and beyond, converging to saturation values of about 1000 and 450 cm2/V s for electrons and holes, respectively. The charge carrier lifetime degradation with increased fluence, due to trapping, is responsible for a predicted charge collection deficit for β particles and for α particles which is found to agree with direct CCE measurements.