Charge collection efficiency studies with irradiated silicon detectors

Small area (1×1 cm2) microstrip detectors, made with a p+-n diode structure on FZ silicon substrates, both with and without oxygen enrichment, have been irradiated with 24 GeV/c protons to fluences of 1.9, 2.9 and 5.1×1014 p/cm2. Their charge collection properties have been studied using a 106Ru beta-source with a wide bandwidth current amplifier and compared with those for a non-irradiated device. The integrated charge collected at different times (10, 25, 40 and 80 ns) has been used to estimate the effect of ballistic deficit. Predictions for the reduction in charge collection efficiency expected at fluences as high as 1015 cm−2 are presented using a parameterization described in earlier work which also fits this data well.