Speaker
Description
4H-SiC Low-Gain Avalanche Detectors (LGADs) are promising for precision timing applications in high-radiation environments because of their wide bandgap, high critical electric field, and low leakage current. In this work, we use Silvaco Victory TCAD to study the effects of radiation-induced defects on the performance of 4H-SiC LGADs.
The study focuses on distinguishing the contributions of gain-layer degradation and radiation-induced bulk defects to the overall performance loss of the detector. Their effects on the effective space-charge distribution and electric-field profile are studied through TCAD simulations, along with the resulting changes in leakage current, avalanche gain, and charge collection efficiency.
Pre-irradiation current-voltage and capacitance-voltage measurements on the fabricated SICAR and ONSEMI 4H-SiC LGAD devices are also performed. The onset of avalanche multiplication near 70~V and 150 to 190~V respectively, is consistent with the TCAD-simulated gain-layer depletion voltages. Several impact-ionization models (Hatakeyama, Konstantinov, Loh) were evaluated against these measured gain curves, and calibrated parameters set was derived to best reproduce the experimental data. This calibrated model is then used as the basis for the radiation-damage simulations.
The simulations cover fluences starting from the $10^{13}$~$\mathrm{n_{eq}/cm^2}$ range and extending towards the early $10^{15}$~$\mathrm{n_{eq}/cm^2}$ range, with different bias voltages used to study the operational gain region after irradiation. At a fluence of $3.5\times10^{13}$~$\mathrm{n_{eq}/cm^2}$, experimental measurements report an approximately 48.5\% reduction in charge collection efficiency. The study aims to quantify the relative contributions of gain-layer and bulk radiation damage and establish a microscopic-to-macroscopic connection between radiation-induced defects and the performance of 4H-SiC LGADs.