Simulation of semiconductor opening switch physics

Semiconductor opening switches (SOS) can interrupt currents at density levels of up to 10 kA/cm/sup 2/ in <10 ns, operate at repetition rates up to 1 kHz, and possess lifetimes of >10/sup 11/ pulses. If stacked, SOS diodes can hold off voltage levels above a few 100 kV. They are therefore ideal for compact high voltage pulse generators of the GW-class for industrial applications. The aim of this work was to improve understanding of the opening process in a semiconductor diode of SOS-type with a doping profile of p/sup +/pnn/sup +/ structure, obtainable through diffusion from the surfaces. To simulate the physical processes inside the diode, the POSEOSS code 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. Using this code, some new interesting results concerning plasma dynamics during the opening process have been found. Using a realistic model for the charge carrier mobility, it was found that the opening process starts first at the n-n/sup +/ boundary. Also it has been possible to derive physical conditions for the occurrence of the SOS-effect. Further improvements seem possible by adapting the SOS device structure to the specific generator circuit. Based on the simulations, a simplified SOS equivalent circuit model has been developed which can be used in circuit simulation programs such as 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.