Charge collection studies of heavily irradiated 3D double-sided sensors

Three-dimensional (3D) photodiode detectors offer advantages over standard planar photodiodes as more radiation hard sensors. 3D detectors with the double-sided geometry have been fabricated as very short strip detectors with the same inter-column spacing as proposed for the ATLAS pixel detector upgrade. The detectors have been irradiated to a fluence of 2 × 10¹⁶ cm^-2 1 MeV equivalent neutrons, which is twice the expected dose of the inner pixel layer of the ATLAS detector for super-LHC operation. Charge collection studies have been performed with analogue readout with 25ns shaping time, as required for (super)LHC experiments. The response of the detectors to Sr-90 electrons is shown and compared with planar devices. The 3D detector is shown to have superior charge collection characteristics even at the highest fluences even when compared to planar devices operating at 1000V, which is in excess of that presently possible in the ATLAS experiment. The experimental results are compared to the simulation of charge transport in the devices.