Speaker
Description
Owing to their unique characteristics, 3D Silicon pixel sensors are the most radiation hard solution for particle tracking in HEP experiments. Both ATLAS and CMS chose to equip the innermost layers of their upgraded trackers at HL-LHC with 3D pixels, and productions are currently under way. Moreover, 3D pixels are also inherently very fast, allowing for remarkable timing performance both before and after irradiation at very large fluences. LHC-b intends to exploit these properties for the second upgrade of its Vertex Detector (VELO2).
In view of future experiments, like FCC-hh, we have started to investigate the possibility to use 4H-SiC for the fabrication of 3D sensors. In fact, Silicon Carbide would allow operation at room temperature with low leakage currents even after extremely large radiation fluences, so that no complex cooling system would be required. Moreover, the very high critical electric field of SiC would also allow to sizably increase the breakdown voltage, which currently represents one of the main problems in 3D Si pixels after irradiation.
As a first step in this activity, we have established a simulation platform, based on the combination of TCAD (Synopsys Sentaurus) and Monte Carlo (AllPix2) simulations, adapting to SiC the approach that we had previously developed for 3D Si pixels. TCAD models for SiC have been validated against experimental results available in the literature for planar sensors. Simulations of 3D pixels have first been implemented with a simplified two-dimensional domain (horizontal slice), before being extended to a more realistic three-dimensional structure.
In this contribution, we will present the initial results from this activity. In particular, two-dimensional distributions of the electrical and weighting potential and field, charge collection efficiency and signal time of arrival will be reported as a function of the active layer resistivity and bias voltage, for different pixel geometries, before irradiation. We are also starting to investigate the post-irradiation performance, based on existing radiation damage model available in the literature, featuring trap levels characteristics of radiation induced defects. Preliminary results will be reported.