A Physical Explanation of Threshold Voltage Drift of SiC MOSFET Induced by Gate Switching

Abstract

Silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs) are regarded as the key device for the next generation of power electronics. However, wide applications are hindered by the threshold voltage instability. How the threshold voltage drifts under both static and dynamic gate stress has been reported. But the underpinning mechanism remains to be revealed, which is the basis of the exploration of the application solutions. This letter is to investigate why the threshold voltage drifts. It is found that the local electric field plays the key role behind the threshold instability, which is a function of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dV</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dt</i> . Based on that, a physical model is proposed and experimentally verified. These findings provide not only a way to understand the mechanism but also a hint of how to mitigate the threshold instability by active gating in power electronics applications.