Characterisation and Optimisation of Radiation-Tolerant Silicon Sensors with Intrinsic Gain

Abstract

The aim of this thesis is to characterise LGADs and DD-APDs before and after irradiation, and study the performance degradation (loss of signal, loss of gain, inhomogeneous spatial response, etc.) as a function of radiation fluence. The origin of the differences in performance is evaluated, and new optimised designs are proposed based on some of the results obtained. The performed work helps understand the fundamental physical processes that are leading to the deterioration of the gain mechanism in silicon devices with intrinsic gain. Whilst aiming for performance optimisation, clear application limits for LGAD and DD-APD devices in terms of radiation hardness are obtained. This thesis sheds light on the many phenomena occurring inside silicon devices after heavy irradiation, both with protons and neutrons. Furthermore, these findings will serve the HL-LHC and other experiments as guidelines for considering the use of devices with intrinsic gain for tracking, calorimetry, or timing applications.