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Reducing the reverse recovery charge (Q rr) is effective for reducing switching loss in field plate (FP)-MOSFETs. A lifetime killer is utilized to reduce Q rr while increasing the leakage current in the off-state. Device simulation shows that a local lifetime killer on the cathode side successfully improves the trade-off between Q rr and I DSS in comparison with that of a uniform lifetime killer. A known issue of cathode lifetime killers is overshoot voltage by hard recovery. However, the overshoot voltage of FP-MOSFET decreases with a cathode lifetime killer owing to an internal snubber, which is a feature of FP-MOSFETs. An internal snubber with a large series resistance causes a dynamic avalanche by both the increase of FP potential and excess carriers in high-speed operation. The cathode lifetime killer also improves dynamic avalanche by excess carriers. Consequently, the cathode lifetime killer is preferable for high-speed FP-MOSFETs because the Q rr–I DSS trade-off and the trade-off between dynamic avalanche and I DSS are effectively improved.

Expansion of a single Shockley stacking fault (SSF) during forward-current operation decreases the reliability of 4H-SiC bipolar devices. We propose a practical method for analyzing the defect evolution of SSF expansion based on free energy according to current density, temperature, and resolved shear stress conditions. The free energy includes chemical potential and elastic strain energy. Specifically, the chemical potential is related to the driving force for the formation of SSFs by temperature and current, and the elastic strain energy corresponds to the driving force for dislocations that form SSFs under the applied stress. It was confirmed that the proposed multiphysics method could well simulate SSF evolution when stress and current were applied. Furthermore, the results suggest that quantum well action, in which electrons in n-type 4H-SiC enter SSF-induced quantum well states to lower the energy of the dislocation system, affects the driving force of SSF formation.

To investigate the mechanism of contraction/expansion behavior of Shockley stacking faults (SSFs) in 4H-SiC p–i–n diodes, the dependences of the SSF behavior on temperature and injection current density were investigated by electroluminescence image observation. We investigated the dependences of both triangle- and bar-shaped SSFs on the injection current density at four temperature levels. All SSFs in this study show similar temperature and injection current density dependences. We found that the expansion of SSFs at a high current density was converted to contraction at a certain value as the current decreased and that the value is temperature-dependent. It has been confirmed that SSF behavior, which was considered complex or peculiar, might be explained mainly by the energy change caused by SSFs.