A comparison of Spice-based and carrier transport based simulations of plasma spread in thyristors

The transient current density distribution in the plane XZ parallel to the electrodes of thyristors and other 4-layer devices is of interest. Since numerical simulations based on the carrier transport equations that include the XZ plane would have to be carried out in 3D, they would become time consuming and expensive. Spice-based XZ simulators as reported in literature are much faster, but the results depend strongly on the necessarily simple equivalent circuits that are used. This paper compares plasma spread simulations in a thyristor, done with an XZ Spice-based simulator previously reported by the authors, with 2D-XY simulations based on the carrier transport equations. It found that for the simulated structure, plasma spread velocity deviates +38% at the beginning of the transient, and -32% near the end of it. On the other hand, for the XZ simulations, it is assumed that the anode current is perpendicular to the XZ plane, and, therefore, the number of discrete elements depend on the extent of validity of that assumption. From the XY simulations it is confirmed that the current flow is almost parallel to the Y direction, making possible high degrees of XZ discretizations.