Practical design of 4H-SiC superjunction devices in the presence of charge imbalance

In the ideal case, superjunction (SJ) drift regions theoretically exhibit a linear relationship between specific-on resistance R on, sp and blocking voltage V BR, but this requires perfect charge balance between the alternating n and p pillars. If any degree of imbalance exists, the relationship becomes quadratic, similar to a conventional drift region, although with somewhat improved performance. In this work, we analyze superjunction drift regions in 4H-SiC under realistic degrees of charge imbalance and show that, with proper design, a reduction in specific on-resistance of 2~ 10x is possible as long as the imbalance remains less than±20%.