Development of Edgeless n-on-p Planar Pixel Sensors for future ATLAS Upgrades

TL;DR

This paper reports on the development and simulation of edgeless n-on-p planar pixel sensors with active edge technology, designed for ATLAS upgrades at HL-LHC, showing promising charge collection efficiency after irradiation.

Contribution

It introduces a novel active edge process for n-on-p pixel sensors and demonstrates its effectiveness through design and simulation for HL-LHC conditions.

Findings

Over 50% charge collection efficiency at 500 V after irradiation

Active edge technology reduces dead area at the sensor edge

Simulation results support the viability of edgeless sensors for HL-LHC upgrades

Abstract

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 $1 \times 10^{15} {\rm n_{eq}}/{\rm cm}^2$ 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 500 V, more than 50% of the signal should be collected in the edge region; this confirms the validity of the active edge approach.