A novel bipolar injection coupled power mosfet (bifet)

Abstract

The Double-Diffused power MOSFET (DMOSFET) and IGBT [ I ] are extensively used in power switching applications. The DMOSFET has fast switching characteristics but has high on-state drop for high voltage applications. The IGBT utilizes bipolar current conduction to achieve a low on-state drop but has slow switching characteristics. When the switching speed of the IGBT is improved by minority-carrier lifetime reduction, its forward drop increases. Consequently, IGBTs with turn-off time less than 250ns are not used in applications. The current conduction capability of other MOS-controlled bipolar transistor structures reported [2-4] is limited by the high on-resistance of the integrated high-voltage driver DMOSFET. This paper describes a new three-terminal device structure called Bipolar-Injection Coupled MOSFET (BIFET) which has a lower on-state drop compared to the DMOSFET while still retaining the fast switching characteristics and high avalanche capability of the DMOSFET.