The turn-off operation of a 4H-SiC gate turn-off thyristor with 2.6 kV breakover voltage has been studied in the MOS-gate mode by means of computer simulation. The turn-off was analyzed at different blocking voltages in the temperature range from 300 to 500 K. A good agreement between the simulation results and experimental data was demonstrated. It is shown that, according to the experiment, for complete turn-off of a thyristor in the MOS-gate mode, the duration of the turn-off pulse applied to the MOSFET gate, Deltat(off), should be long enough (Deltat(off) > Deltat(off)*), where Deltat(off)* is the minimum duration of the turn-off pulse. The Deltat(off)(*) value depends rather weakly on the cathode blocking voltage V-0, despite the strong dependence of the critical charge density on V-0. It is shown that the long delay in the spontaneous switch-on, occurring at Deltat(off) less than or equal to Deltat(off)* is due to the very slow current rise at low injection level in the blocking p(0)-base. An analytical theory of the current rise processes has been developed for the case when the current injection coefficients of the emitter-base junctions are not unity. (C) 2002 Elsevier Science Ltd. All rights reserved.