Performance Limit and Design Guideline of 4H-SiC Superjunction Devices Considering Anisotropy of Impact Ionization

Superjunction (SJ) structure is one of the most effective approaches to improving the performance limit between specific ON-resistance ( ${R}_{\text {on,sp}}$ ) and breakdown voltage ( $\textit {BV}$ ) for the unipolar power device, particularly in high-voltage and high-current areas. In this letter, ${R}_{\text {on,sp}}-\textit {BV}$ performance limit of 4H-SiC SJ drift region is achieved featuring both the two-dimensional electric field and the anisotropy of impact ionization of 4H-SiC. The breakdown path is the curve from the bottom midpoint of N pillar to the top midpoint of P pillar via the midpoint of P-N pillar interface, instead of the midline of the pillar, due to that the impact ionization along [ $11~\overline {{2}}~0$ ] is stronger than that along [0001]. Moreover, a design guideline is provided for optimized ${R}_{\text {on,sp}}$ ( ${R}_{\text {on,opt}}$ ) under a given $\textit {BV}$ , including the width, depth, and concentration of SiC SJ drift region. SJ adoption enables SiC drift region to have a quasi-linear dependence of ${R}_{\text {on,sp}}$ on $\textit {BV}$ , i.e., ${R}_{\text {on,sp}}\propto \textit {BV}^{{1.007}}$ , which is well verified by TCAD simulation. With $\textit {BV}$ larger than 2000V, the SJ utilization can significantly reduce ${R}_{\text {on,sp}}$ of SiC device. By determining the breakdown path, the theoretical performance limit shows huge potential of SJ approach for the high-voltage and high-current SiC device, and the practical design guideline can instruct to better design the SiC SJ device.