Silicon radiation detectors in 3D technology at high speed and low energy consumption.

Abstract

In the last few years, there has been increased emphasis on silicon radiation detectors due to their importance for a wide range of industrial, medical and scientific applications. Unlike planar technology, the use of the 3D one in the fabrication of these kind of detectors offers advanced performances. The exploitation of the third dimension within the silicon substrate in the case of planar detectors actives its volume to be terminated physically and electrically without dicing. The first goal of this thesis is to enables the dead area reduction of an existing X-ray imaging detector for the free-electron laser facilities and obtaining the required high breakdown voltage under all conditions (⁓ 500 V). In 3D detectors case, the columns electrodes penetrate vertically in the bulk. As a result, the active volume is decoupled from the inter-electrode distance causing a lower depletion voltage and trapping probability, reducing the power dissipation and minimizing the inter pitch charge sharing. This makes them a very tempting choice for the future High luminosity Collider (HL- LHC) upgrades, where they should withstand very large particle fluences up to (2×1016 neq cm-2). 1-MeV equivalent neutrons. The second goal of this thesis is predicting the leakage current and charge collection efficiency (CCE) of small-pitch 3D sensors using TCAD simulation. The considered devices are irradiated at large fluences up to the maximum value foreseen at the innermost pixel layers at HL-LHC (2×1016 neq cm-2). Results are compared with experimental data from 3D diodes measured with a position resolved laser system in order to predict high signal efficiency and charge multiplication effects at high voltage, investigating the different distribution of the electric field, in particular to presence/intensity of the double peak.