Observation of full charge collection efficiency in heavily irradiated n+p strip detectors irradiated up to 3×10 15 n eq/cm 2
In this work we report measurements of signals caused by fast electrons from a 90Sr source detected by n-type readout strips implanted in p-type bulk silicon, read out with a SCT128 chip. Charge collection measurements with detectors irradiated with reactor neutrons up to 1016neq/cm2 were performed up to very high reverse bias voltages of over 2000V. The most probable value of collected charge measured with detectors irradiated up to 3×1015neq/cm2 was as high as that measured before irradiation. Detectors irradiated to 1016neq/cm2 also exhibited very good performance. Because of the large resistance of the heavily irradiated silicon detectors they can be biased with a high forward voltage, allowing charge collection measurements to also be performed in the forward bias mode of operation. Simulations of charge collection in an irradiated detector were compared to measurements.