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The temporal and spatial evolution of patterns in physical systems due to electrical current flow can be described for a certain class of systems, which includes certain semiconductor and gas discharge systems, by a two-layer model in terms of the electrical current density and the electrical potential. An equation for the nonlinear layer is derived, the characteristic parameters of which can be obtained from experiments at the respective systems without inhomogeneous patterns lateral to the main current direction. The resulting equation takes into account diffusion and drift effects in the nonlinear layer. It turns out that the drift effects occur only if there is a "net space charge. " Two special cases are derived depending on which of the two layers gives the main contribution to the displacement current density, and the typical static and dynamic behavior is studied by numerical calculations. Furthermore, the application of the model to rea1 devices is discussed, and a comparison is made with experimental results obtained with a dc glow-discharge system.

Spatial and spatio-temporal patterns of the current density and the potential distribution in silicon pnpn devices are experimentally investigated. In dependence on various parameters we observe homogeneous current distributions and the spontaneous appearance of stationary standing, rocking, and travelling well-localized current density filaments. Model calculations reproduce the main features of the experiments.In Silizium pnpn-Dioden wird das raumliche und raum-zeitliche Verhalten der Stromdichte und der Oberflachenpotentialverteilung experimentell untersucht. In Abhangigkeit von verschiedenen Systemparametern kann man raumlich homogene Stromdichteverteilungen sowie stabile stationare, schaukelnde und wandernde lokalisierte Stromdichtefilamente beobachten. Modellrechnungen reproduzieren qualitativ die experimentellen Ergebnisse.

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This paper gives an overview of the physics and electrical characteristics of irradiation-induced defects in silicon created by electrons, protons, and helium ions. The parameters of the traps usable as recombination centers or causing doping and discharging effects are described quantitatively, including temperature dependence and injection level dependence. The influence of recombination centers on the electric characteristics of power devices is discussed, especially with respect to applications for mediumvoltage and high-voltage power devices.