MOS GTO - A turn off thyristor with MOS-controlled emitter shorts

The use of integrated MOS-controlled emitter shorts is a new method to turn off high power thyristors without any additional base contacting system. Simulations of the MOS GTO turn off process show that on state currents in the order of 1000 A/cm²can be turned off. Samples of 3.5 mm × 3.5 mm MOS GTOs both with p-channel and n-channel MOS-structures have been prepared. p-base doping, lifetime reduction by Pt-diffusion, width of the emitter element ard Ronof the integrated MOS transistors were optimized with respect to turn off and on state characteristics. With the optimized devices at anode voltage less than about 200 V a current of about 1000 A/cm²could indeed be turned off.