Anode current limiting effect of high power GTOs

An abrupt increase in the on-state voltage occurs drastically at a certain anode current for a high power GTO with an extremely low p-base sheet resistance. From measurements on potential distribution for such devices, it was found that the most significant fraction of the voltage drop occurs across the center junction. As a result of a series of experiments on GTOs and transistors with various doping profiles, the critical anode current was shown to increase by decreasing a p-base impurity concentration CPJ1near the cathode-gate junction. This result leads to a conclusion that decreasing CPJ1improves the surge on-current capability for GTOs.