Speaker
Description
Good spatial and timing resolution in tracking systems for future High-Energy Physics experiments requires a good understanding of the mechanisms that cause sensor performance degradation under extreme irradiation.
A batch of p-in-n Low-Gain Avalanche Diode (LGADs) has been manufactured by the Fondazione Bruno Kessler (FBK), with a highly doped signal multiplication layer formed using n-type dopants (nLGADs) within a 55 µm-thick substrate. A novel design with a p++ ohmic contact and n+ gain implant accounting for the activation and diffusion of the gain layer dopants. The nLGAD batch features fourteen such wafers, varying by doping concentration, type of dopant (phosphorus or arsenic), diffusion, and implantation depth. The donor removal mechanism responsible for gain degradation due to irradiation is studied for nominal dopant concentrations of ~10$^{16}$ atoms/cm$^{2}$. This is investigated by irradiating subsets of the nLGAD devices with neutrons up to fluences of 1$\times$10$^{15}$ n$_{\rm{1~MeV~eq}}$ cm$^{-2}$ at the Jozef Stefan Institute in Ljubljana.
Key results from the characterisation of these sensors include donor removal rates performed in the Torino laboratory, and timing performances both before and after irradiation using a plethora of ionising sources such as the 4 GeV/c electron beam at the DESY Test Beam Facility, the CERN SPS proton and pion beam, measurements with a $^{90}$Sr β source, and a ~ 5 keV X-ray source. These will also be supported by gain studies with 1060 nm IR, 404 nm blue, and 375 nm UV laser measurements with an SPA-TCT setup, and charge carrier information extracted in a TPA-TCT apparatus.
Alongside previous studies on the acceptor removal rate in the eXFlu batch of n-in-p LGADs, the results provide insight into the p+-n+ compensated LGAD designs of the CompleX1 batch of sensors. The design, simulations, and preliminary results of the CompleX1 batch will also be presented in the context of radiation tolerance on the path to refining pixel sensors optimised for operation at fluences up to ~1$\times$10$^{16}$ n$_{\rm{1~MeV~eq}}$ cm$^{-2}$ and beyond.