Gate Switching Instability in Silicon Carbide MOSFETs—Part II: Modeling

It has recently been observed that bipolar switching between accumulation and inversion can result in an unexpected threshold voltage drift in SiC MOSFETs. This phenomenon has been termed gate switching instability (GSI) and is characterized by power-law time exponents close to unity, significantly larger than what is typically observed for ordinary bias temperature instability (BTI) during static or unipolar switching stress. Since the bias, frequency, and temperature dependence of GSI are the same as what is seen in charge pumping (CP) experiments, we stipulate that recombination events at the interface lead to recombination-enhanced defect reactions (REDRs), which can eventually lead to degradation. Based on these observations, we develop a comprehensive physical model for GSI, discuss its features, derive a closed form analytical solution, and finally validate the model against detailed experimental data.