Characterisation of low gain avalanche detectors for the CMS experiment

Abstract

The aim of this thesis was to measure the current-voltage and capacitance-voltage characteristics of the latest batch of Ultra-Fast Silicon Detectors produced by Fondazione Bruno Kessler and evaluate the parameters of the detectors, such as the breakdown voltage, the full depletion voltage, the leakage current and the capacitance. The paper describes the principle of operation of silicon detectors, considers factors affecting the timing performance of sensors, and also highlights the critical features of UFSD. In the experimental part of the work, the I-V and C-V characteristics for two groups of UFSD samples are presented. Two groups differed in the concentration of acceptors in p-stop, the layout of p-stop, and the distance (the inter-pad gap) between the active regions of the sensor; the C-V method for calculating the doping profile within a detector is presented. The experimental study of the detectors was performed in the Detector Laboratory at the Helsinki Institute of Physics.