Evidence of enhanced signal response at high bias voltages in planar silicon detectors irradiated up to 2.2×1016 neq cm−2

The signal generated by minimum ionising particles in segmented planar silicon sensors irradiated to hadron fluences exceeding 2×1016 neq cm−2 has been measured with 40 MHz clock speed analogue electronics. The results show a surprisingly high signal after these doses, well above the maximum expected charge predicted by the trapping of charge carriers at radiation induced defect centres. The ability of irradiated sensors to withstand high bias voltages allows for the collection of a substantial signal that is sometimes higher than the signal measured before irradiation.