Numerical analysis on abnormal thyristor forward voltage increase due to heavy doping in gated p-base layer

Abstract

An abnormal forward voltage increase was observed for a p-base gated double diffused n + pn − p + high power thyristor with high impurity concentration at the n +- p emitter-base junction. Accurate numerical analysis shows that heavy doping effects are the most responsible mechanism for the abnormality and that depletion layer formation at the center junction accompanies it. It will be shown that appropriate control of the impurity concentration at the emitter-base junction is necessary to avoid this abnormality by realizing the common base transistor current gain of greater than 0.73 for n + n −-portion.