The Effect of Charge Imbalance on Superjunction Power Devices: An Exact Analytical Solution

Charge imbalance in the drift region of superjunction (SJ) devices can significantly impair its breakdown voltage (BV). An analytical solution for the electric field and the BV of symmetrical SJ devices, which accounts for the effect of the charge imbalance, is proposed in this letter. The resulting equations are particularly simple and meaningful. They provide valuable insight into the effect of charge imbalance. A comparison of the analytical results with 2-D numerical simulations shows that the proposed model for symmetrical SJ devices can accurately predict the electric field distribution and the reduction in the BV due to charge imbalance in the drift layer.