A time-and temperature-dependent simulation of the GTO turn-off process

New insight into the GTO thyristor turn-off process has been obtained by performing an exact two-dimensional time- and temperature-dependent numerical simulation. Novel numerical solution techniques for faster convergence enable efficient modeling of high voltage operation as well as simultaneous electrical and thermal solutions. It was found that an additional current term relating to bandgap variation with temperature should be included. The model was applied to a 200 mX5mm emitter GTO. A large current 34A(3,400A/cm²) was turned-off by 6A of gate current. The peak current density, 17,000A/cm², was reached during the falltime transient. The final on-region width (<50 m) was found to be a decreasing function of lateral gate current density. When the total anode current is high, an initial anode voltage increase is caused by the confinement of the on-region to a narrow area. The maximum applied voltage for the current crowded area was also found to be restricted by a mechanism similar to punch-through.