In-depth analysis of SiC GTO thyristor performance using numerical simulations

We present device characteristics obtained from two-dimensional numerical s imulations of asymmetric 4H-SiC gale turn-off (GTO) thyristor structures. M aterial parameters are discussed, and a good comparison with measured resul ts is demonstrated. Current vs voltage characteristics indicate that typica l structures have quite good electron injection from the cathode, but hole injection from the anode is weak unless the n-base layer is doped less than 1 x 10(18) cm(-3). On the other hand, lowering electron injection at the c athode/p-base junction is important to improve the turn-off gain. The 2000 V blocking structure simulated with lifetimes of tau(n):tau(p) = 100:50 ns does not reach its on-state for current densities less than 6000 A/cm(2) bu t for lifetimes of 400:200 ns, this minimum is reduced to 1 A/cm2. Blocking voltages increased approximately 400 V for a 3 mu m increase in the drift region length. Clamped inductive load mixed-mode simulations with a 4H-SiC flyback diode indicate that the peak power during turn-on is only slightly higher than during turn-off when switching a 4 Omega, 5 mH load. Because tu rn-on times are much shorter than turn-off times, much less power is dissip ated during turn-on for both 27 degrees C and 200 degrees C ambient tempera ture operations. (C) 2000 Elsevier Science Ltd. All rights reserved.