Cathode short structure to enhance the robustness of bidirectional power MOSFETs

Bidirectional power MOSFETs can block voltages of either polarity between the drain and the source. This makes them attractive for many applications as they offer a distinct cost advantage over the conventional power MOSFETs. However, bidirectional power MOSFETs suffer from poor robustness as the parasitic bipolar is easier to trigger when the body is routed out separately from the source. In this paper, we propose and demonstrate the concept of a cathode short which reduces the parasitic bipolar gain by degrading the injection efficiency of the base-emitter junction and consequently improves the robustness of the bidirectional power MOSFET. The parasitic bipolar gain is shown to reduce by more than a factor of 3 and the current switching capability is enhanced by a factor of ~4.