Design of Dual-Gate Superjunction IGBT towards Fully Conductivity-Modulated Bipolar Conduction and Near-Unipolar Turn-Off

Abstract

In this work, we propose to utilize a superjunction structure as a controlling port for the strength of conductivity modulation inside the IGBT, so that a low V ON is obtained by a strong conductivity modulation during on-state and a near-unipolar turn-off is achieved by removing the minority carriers before turn-off event. For this purpose, a dual-gate superjunction IGBT (DG-SJ-IGBT) is designed and studied by numerical TCAD simulations. An auxiliary gate in the DG-SJ-IGBT disconnects the p-pillar during on-state, enabling full conductivity-modulated bipolar conduction and a consequent low V ON . As a well-known issue, conductivity modulation is accompanied by significant additional turn-off loss (E OFF ). To overcome this issue, the DG-SJ-IGBT takes advantage of the p-pillar which extends through the entire drift region. Before the turn-off event, a negative bias on the auxiliary gate builds up a hole inversion layer which electrically grounds the p-pillar to the p-body. The grounded p-pillar serves as a hole extractor, suppresses the minority density throughout the depth of the drift region, and brings the device into a near-unipolar conduction mode. Thus, a near-unipolar turn-off can be obtained, resulting in a low E OFF .