Numerical analysis of blocking characteristics for thyristors

Blocking characteristics of high power thyristors are calculated and analyzed by solving the full set of one-dimensional semiconductor device equations numerically. It is found that the hole injection efficiency is small and the current amplification is limited by the injection efficiency rather than by the transport factor, contrary to the conventional assumption for high power thyristors. The effective avalanche multiplication factor is larger than the multiplication factor Mpfor holes because of the contribution of the generated carriers in the depletion region, and the conventional assumption employing Mpfor the multiplication factor gives the value of the leakage current considerably smaller than the exact one. The increase in the leakage current with decreasing n-base width is caused by the increase in the injection efficiency.