Charge Imbalance Tolerance of 4H-SiC Superjunction Devices Featuring Breakdown Path Variation

In this letter, the impact of charge imbalance on silicon carbide (SiC) superjunction (SJ) device is studied thoroughly. The breakdown path variation under different degrees of charge imbalance is revealed for the first time by joint analysis of the SiC anisotropy of impact ionization and the charge-imbalanced SJ two-dimensional electric field distribution. Primarily due to this anisotropy, it is a significant finding that the breakdown voltage could be even higher than the balance case when either P or N pillar is slightly under-doped. Furthermore, an SJ design methodology is proposed based on figure-of-merit (FOM) sensitivity and process tolerance, which guides how to better design low-sensitivity SJ devices within a certain range of charge imbalance degree. It is indicated that the wide pillar is suggested for large process tolerance and the under-doped case is less sensitive to charge imbalance than the over-doped case. In brief, the aforementioned revelation can gain new physics-level insights into various charge-imbalanced SJ cases and the methodology can achieve not only the high FOM based on practical process capability but also the required process tolerance based on target performance.