Investigating ultra-thin 4H-SiC AC-LGADs for superior radiation-hard timing applications

TL;DR

This paper explores ultra-thin 4H-SiC LGADs for high-radiation timing applications, demonstrating their superior charge collection and timing performance under intense irradiation conditions, with potential for sub-25 ps resolution.

Contribution

It introduces 4H-SiC LGADs as a promising radiation-hard alternative to silicon, showing their advantages in gain retention and timing performance at high fluences.

Findings

4H-SiC LGADs outperform silicon and diamond in high-fluence environments.

A 20 μm thick 4H-SiC sensor achieves sub-25 ps timing resolution.

Simulation results align well with experimental irradiation data.

Abstract

The Low Gain Avalanche Diodes (LGADs) are promising particle detectors for timing resolution better than $50$ ps under a high radiation environment. This study investigates n-in-p LGAD architecture, focusing on ultra-thin sensors of thickness less than $50\ \mu$m using the WeightField2 program. The capabilities of WeightField2 are demonstrated by comparing its results with irradiation measurements from an FBK LGAD wafer, showing good agreement across unirradiated and neutron-irradiated conditions. This paper presents device simulations in High Luminosity LHC conditions (lifetime integrated fluence $ \mathcal{O} (10^{14})\ \mathrm{n_{eq}~cm^{-2}}$, temperature $ \approx 243\ \mathrm{K} $), and taking into account radiation damage, gain reduction due to fluence, and lattice defects. It is shown that a 20 $\mu$m thick sensor achieves the best timing performance. Among Silicon (Si), Diamond (C), and 4H-Silicon Carbide (4H-SiC), we found 4H-SiC to be the most promising: it provides the highest gain value for a fixed thickness and gain implant layer configuration, and best retains high charge collection value and timing capability under increasing fluence up to $50\times10^{14}\ \mathrm{n_{eq}~cm^{-2}}$. A time resolution less than 25 ps is reported with different gain implant concentrations for a $20 \mu$m 4H-SiC sensor. This work presents the potential of SiC-based LGADs in high-radiation collider environments.