Numerical investigation of the thyristor forward characteristic

Analytical solutions for the forward characteristic of thyristors have been presented in the literature. All of them are limited to abrupt and constant doping profiles. Average values for the mobilities and the carrier lifetime have to be assumed for each region of the device. Results will be presented here which are based on an exact numerical solution of the transport, continuity and Poisson equations for the one-dimensional thyristor. Doping, mobility and lifetime can be varied from point to point. Thyristor structures are much longer and higher doped than the devices treated numerically in the literature. The number of iterations necessary to obtain an exact solution can still be kept within reasonable limits by starting from an analytical solution. For this a new analytical approximation for the space charge layers under high injection conditions had to be developed. The dependency of the forward characteristic on various device parameters was examined, and the important results were verified experimentally.