Improvement in Trade-Off between Turn-Off Time and Other Electrical Characteristics of Fast-Switching Thyristors

Abstract

Trade-offs between turn-off time, on-state voltage and reverse blocking voltage should be improved in producing fast-switching thyristors with higher blocking voltage and current handling capabilities. It is well known that the electrical characteristics of a thyristor depend strongly on the gold distribution in its nB layer. The influence of a boron-diffused layer on the gold distribution in a silicon wafer has been investigated. It has been found that the gold distribution gradient in the central region of the wafer is varied by the existence of a highly-concentrated layer of boron on one side of the wafer, and that if this phenomenon is applied to the production of thyristors, the trade-offs between turn-off time, on-state voltage and reverse blocking voltage are greatly improved. Further, the effect of the gold distribution gradient on the turn-off time, on-state voltage and reverse leakage current is discussed theoretically.