  In this radiation tolerance study, Low Gain Avalanche Detectors (LGADs) with
a carbon-enriched broad and shallow multiplication layer were examined in
comparison to identical non-carbonated LGADs. Manufactured at IMB-CNM, the
sensors underwent neutron irradiation at the TRIGA reactor in Ljubljana,
reaching a fluence of $1.5e^{15} {n_{eq}} cm^{-2}$. The results revealed a
smaller deactivation of boron and improved resistance to radiation in
carbonated LGADs. The study demonstrated the potential benefits of carbon
enrichment in mitigating radiation damage effects, particularly the acceptor
removal mechanism, reducing the acceptor removal constant by more than a factor
of two. Additionally, time resolution and collected charge degradation due to
irradiation were observed, with carbonated samples exhibiting better radiation
tolerance. A noise analysis focused on baseline noise and spurious pulses
showed the presence of thermal-generated dark counts attributed to a too narrow
distance between the gain layer end and the p-stop implant at the periphery of
the pad for the characterized LGAD design; however, without significant impact
of operation performance.
