Impact of Neutron Irradiation on LGADs with a Carbon-Enriched Shallow Multiplication Layer: Degradation of Timing Performance and Gain

TL;DR

This study investigates how neutron irradiation affects LGAD sensors with a carbon-enriched shallow multiplication layer, showing improved radiation resistance and reduced degradation compared to non-carbonated LGADs.

Contribution

It demonstrates that carbon enrichment in LGADs significantly mitigates radiation damage, especially in reducing acceptor removal and maintaining timing performance.

Findings

Carbon-enriched LGADs show less acceptor removal.

Radiation tolerance is improved with carbon enrichment.

Timing performance degrades less in carbonated LGADs after irradiation.

Abstract

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.