Lab and test beam results of irradiated silicon sensors with modified ATLAS pixel implantations

In Dortmund, planar silicon pixel sensors were designed with modified n+-implantations and produced in n+-in-n sensor technology. Baseline for these new designs was the layout of the IBL planar silicon pixel sensor with a 250 μm × 50 μm pitch. The different implantation shapes are intended to cause electrical field strength maxima to increase charge collection after irradiation and thus increase particle detection efficiency. To test and compare the different pixel designs, the modified pixel designs and the standard IBL design are placed on one sensor which can be read out by a FE-I4. After irradiation with protons and neutrons respectively the performance of several sensors is tested in laboratory and test beam measurements. The presented laboratory results verify that all sensors are fully functional after irradiation. The the test beam measurements show different results for sensors irradiated to the same fluence with neutrons in Sandia compared to sensors irradiated with neutrons in Ljubljana or with protons at CERN PS.