Modeling of oxygen-vacancy hole trap activation in 4H-SiC MOSFETs using density functional theory and rate equation analysis

Abstract

A plausible Density Functional Theory (DFT)-based Oxygen Vacancy (OV) hole trap activation model was recently proposed to explain the High Temperature-Gate Bias (HTGB) stress-induced additional threshold voltage instability in 4H-Silicon Carbide (4H-SiC) power MOSFETs. In this model, certain originally electrically ‘inactive’ OVs were shown to structurally transform over time to form switching oxide hole traps during HTGB stressing. Here, we use this model to perform transient simulation of the buildup of hole-trapped OVs in HTGB-stressed 4H-SiC power MOSFETs. This is shown to correlate well with the recently observed excessive worsening of threshold voltage instability in HTGB-stressed 4H-SiC power MOSFETs. This helps to validate the role of OVs in the degradation of high-temperature reliability of these devices.