TCAD modeling of radiation-induced defects in 4H-SiC diodes

TL;DR

This paper develops a TCAD model for 4H-SiC diodes that accurately predicts radiation-induced performance degradation, including electric field changes and charge collection loss, based on experimental neutron irradiation data.

Contribution

It introduces a comprehensive bulk radiation damage model for 4H-SiC diodes, incorporating new defect clusters and validating predictions against experimental measurements.

Findings

Model predicts electric field shifts and capacitance flattening.

Degradation in charge collection efficiency under irradiation.

Identification of EH4 defect cluster as a key lifetime killer.

Abstract

Silicon Carbide (SiC) has several advantageous properties compared to Silicon (Si) that make it an appealing detector material, such as a larger charge carrier saturation velocity, bandgap, and thermal conductivity. While the current understanding of material and model parameters suffices to simulate unirradiated 4H-SiC devices using technical computer-aided design (TCAD), configurations to accurately predict performance degradation after high levels of irradiation due to induced defects acting as traps and recombination centers do not exist. Despite increasing efforts to characterize the introduction and nature of such defects in 4H-SiC, published results are often contradictory. This work presents a bulk radiation damage model for TCAD simulations based on measurements on 50 $\mu m$ 4H-SiC pad diodes, neutron-irradiated at various fluxes ranging from $5\times 10^{14}$ $n_{eq}/cm^2$ to $1\times 10^{16}$ $n_{eq}/cm^2$. The model accurately predicts internal electric shifts, such as flattening of the detector capacitance, degradation in charge collection efficiency (CCE), and signal detection capabilities under forward bias conditions up to high bias. It further introduces the EH$_4$ defect cluster as major lifetime killer and reinforces the assumption of the EH$_{6,7}$ deep-level defect to be of donor type.