Simulation of Semiconductor Opening Switch Physics
A. Engelko, H. Bluhm
Forschungszentrum Karlsruhe, Institut für Hochleistungsimpuls- und Mikrowellentechnik, P.O. Box 3640
D-76021 Karlsruhe, Germany
Semiconductor opening switches (SOS) are able to interrupt currents at density levels of up to 10 kA/cm² in less than 10 ns, operate at repetition rates up to 1 kHz, and possess lifetimes of more than 1011 pulses. 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, obtainable through diffusion from the surfaces. 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. Applying the code some new interesting results concerning the plasma dynamics during the opening process in the switch have been found. Especially, using a realistic model for the charge carrier mobility, it was found that the opening process starts first at the n-n+ boundary. Also it has been possible to derive the 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 simulation results 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.
13th IEEE Pulsed Power Conf., Las Vegas, Nev., June 17-22, 2001