Development of edgeless n-on-p planar pixel sensors for future ATLAS upgrades

The development of n-on-p ‘‘edgeless’’ planar pixel sensors being fabricated at FBK (Trento, Italy), aimed at the upgrade of the ATLAS Inner Detector for the High Luminosity phase of the Large Hadron Collider (HL-LHC), is reported. A characterizing feature of the devices is the reduced dead area at the edge, achieved by adopting the ‘‘active edge’’ technology, based on a deep etched trench, suitably doped to make an ohmic contact to the substrate. The project is presented, along with the active edge process, the sensor design for this first n-on-p production and a selection of simulation results, including the expected charge collection efficiency after radiation fluence of 1x10^15 neq/cm^2 comparable to those expected at HL-LHC (about ten years of running, with an integrated luminosity of 3000 fb^-1) for the outer pixel layers. We show that, after irradiation and at a bias voltage of 500V, more than 50% of the signal should be collected in the edge region; this confirms the validity of the active edge approach.