dV/dt effect in high-voltage (1.5 kV) 4H–SiC thyristors

The switching of high-voltage (1.5 kV) 4H–SiC gate turn-off thyristors (GTOs) by the dV/dt effect has been studied in the temperature range from 300 to 504 K. At a 30 ns rise time of the forward bias V(t), the characteristic bias at which the structure under investigation can be switched on by the dV/dt effect decreases steadily from 289 V at room temperature (dV/dt ∼ 9.7 kV/μs) to 137 V at T = 504 K. The characteristic critical charge per unit area, Qcr, equal to 1.9 × 10−7 C/cm2 at room temperature, also decreases steadily as the temperature increases. The main physical mechanisms that contribute to Qcr formation and the temperature dependence of the critical charge are qualitatively analyzed. The influence exerted by two-dimensional processes on the dV/dt switching is examined by making analytical estimates and using a computer simulation. The results obtained agree well with experimental data.