Physical insight into turn-on transient of silicon carbide gate turn-off thyristor

Silicon Carbide (SiC) Gate Turn-off (GTO) thyristor is regarded as a promising option for pulsed power applications; however, the formation of high di/dt has been constrained by the slow current rise transient phase and the turn-on current heterogeneity over the chip device. In this paper, a practical integrated multi-cell simulation is performed to physically characterize the turn-on transient of SiC GTO thyristor. Through examining electrical coupling between adjacent cells caused by both parasitics of electrode metallization and carrier travelling via SiC, the current distributions are observed, and the carrier transport dynamics are analyzed in detail. Furthermore, physical mechanisms dominating the current heterogeneity among multi-cells are discovered in depth. It is revealed that the current heterogeneity during the turn-on transient is primarily resulted from the Gate signal delay caused by the Gate Runner metallization, and the lateral interaction from adjacent semiconductor regions adds to this inhomogeneity; however, this situation can be improved once the electrical distance between each Anode contact and the Anode electrode gets lowered. Design method for turn-on performance improvement is also proposed accordingly. Besides, based on the analysis conducted on the multi-cell simulation results, the possible reason of the extremely slow current rise transient phase is speculated and experimentally verified. The improvement in the comprehension of SiC GTO's turn-on transient, which cannot be obtained from the traditional investigation from the viewpoint of one elementary cell, will provide guiding principles helping in directing future efforts to advance the improvement of device design technology.