Adolf Herlet

The forward characteristic of silicon power rectifiers at high current densities

Abstract The Hall theory of the pin -rectifier is extended by considering the diffusion currents in the heavily doped regions, and a general solution with low-level injection in the exterior p - and n -regions and with high-level injection in the middle region is derived. At small current densities, this general solution passes into the Hall solution: for high current densities an approximate quadratic I–V dependence is found. The dependence of the forward characteristic within this range upon the properties of the heavily doped regions and of the middle region is discussed in detail.

The maximum blocking capability of silicon thyristors

Abstract The blocking capability of thyristors in forward and reverse direction is discussed under such aspects as they are of interest especially for the design of power thyristors. As in the ideal case the blocking capabilities in both directions ought to be equal, the considerations are confined at first to the simpler evaluation of the reverse blocking capability, and to this end a quantitative method is developed. The influence of certain thyristor parameters on the dependence of the blocking capability upon the resistivity of the starting material is considered. Finally, the conditions for the ideal case of identical blocking capabilities in forward and reverse directions are explained, and the steps to be taken in order to realize it are mentioned.

Forward characteristics of thyristors in the fired state

Abstract The forward voltage of thyristors in the fired state is discussed from points of view which are especially relevant for power thyristors. With big forward currents, i.e. with high level injection in both base regions, the forward voltage of a thyristor should become identical with that of a pin rectifier of equal dimensions. This is verified by experiment; it is furthermore shown that the forward voltage is independent of the doping level in the base regions. For the difference of the forward voltages of both devices found with low current densities a simple approximate relation is derived and substantiated by experiment. The carrier lifetime with high injections is found to be independent of the doping level in these experiments; this was affirmed, too, by former measurements.