Charge Sheet Super Junction in 4H-Silicon Carbide

SuperJunctions (SJs) have long been realized in Si. However, their fabrication in 4H-Silicon Carbide (SiC) has been problematic because of poor control of the p-dopant activation efficiency in SiC. We propose that this problem related to SiC material be overcome using a version of SJ called Charge Sheet SJ (CSSJ) which we proposed in the context of Si material a decade ago. In CSSJ, the p-pillar is replaced by an insulator such as Al2O3 which has a fixed negative charge at its interface with the SiO2 used as a liner before depositing Al2O3 this negative charge simulates the ionized p-dopants, and can be easily controlled via the Al2O3 deposition temperature. Also, it may be easier to deposit an insulator rather than realize a p-pillar, in a high aspect ratio trench. We build the motivation for fabricating the CSSJ in SiC by outlining its possible fabrication steps, and reporting its TCAD simulations for pillars of 5 μ m width, 18 μ m length and 2-8× 1012cm-2 charge. We find that the 4-H SiC CSSJ can have 40% lower specific on-resistance and up to 15% higher breakdown voltage than an SJ. Further, as compared to CSSJ in Si, the breakdown voltage of a CSSJ in SiC is > ten times less sensitive to pillar charge imbalance arising from process variations.