Simulation of semiconductor opening switch physics

Abstract

Summary form only given. Semiconductor opening switches (SOS) are able to interrupt currents at density levels of up to 10 kA/cm2 in less than 10 ns. If stacked, SOS diodes can hold off voltage levels above a few 100 kV. They are therefore ideal for the design of compact high voltage pulse generators of the GW-class for industrial applications. The aim of this work was to improve our understanding of the opening process in a semiconductor diode of SOS-type with a doping profile of p+pnn+ structure. To simulate the physical processes inside this diode the code POSEOSS was developed. It contains a detailed physical model of charge carrier transport under the influence of density gradients and electric fields and considers all relevant generation and recombination processes. It possess a large degree of flexibility and allows to carry out parameter studies to determine the influence of different physical quantities, like doping and impurity levels. Applying the code, using realistic values for the charge carrier mobility, it was found that the opening process starts first at the n-n+ boundary, in contradiction to results published by other authors. Based on the simulation results a simplified SOS equivalent circuit model has been developed which can be used in the circuit simulation program PSpice. A new pulse generator scheme based on inductive stores is proposed, in which power multiplication is achieved by unloading the inductors, previously charged in series, in parallel. This scheme can be considered as the inductive equivalent of a Marx generator. We present Pspice simulations of such a scheme based on semiconductor opening switches. The theoretical results were compared to measurements obtained with a simple experimental set-up using two 100 kV SOS-switches. The measurements showed good agreement with the simulation results. Further improvements seem possible by adapting the SOS device structure to the specific generator circuit.