4.5-kV injection-enhanced gate transistors (IEGTs) with high turn-off ruggedness

Although high blocking voltage insulated gate bipolar transistors (IGBTs) have wider safe operating areas (SOAs) than do gate turn-off thyristors, a failure problem remains at turn-off transient. The purpose of this paper is to clarify the mechanism of failure at turn-off transient and to develop a high-voltage injection-enhanced gate transistors (IEGTs) with wide SOA at turn-off transient [wide reverse-biased SOA (RBSOA)]. We discuss this destruction mechanism in detail on the basis of comparison of experimental results with calculated results obtained by an analytical model considering dynamic avalanche generation. These results lead to the conclusion that the design of the n-emitter and the control of avalanche generation onset are key parameters for realizing high ruggedness of high-voltage IEGT. Based on the proper design of the n-emitter and the gate driving condition, a high-voltage and high-current 4.5-kV IEGT with wide RBSOA, keeping low saturation voltage and low turn-off switching loss, has been successfully developed.