Objective

The objective of the project has been the numerical and theoretical analysis of self-organized spatiotemporal patterns in bistable and multistable semiconductor systems. Our aim has been to influence, control and select such patterns. Various semiconductor nanostructures like the resonant tunneling diode (DBRT = Double Barrier Resonant Tunneling Diode), the superlattice, as well as the HHED (= Heterostructure Hot Electron Diode), which have been studied by our group for a long time, have served as model systems. The modelling of the nonlinear electronic transport was done on the level of semiclassical electron density dynamics. This leads to reduced model equations, very similar to those of reaction-diffusion systems, which are studied intensely in the framework of other projects of Sfb 555. Therefore our research also has a fundamental, methodical character far beyond semiconductor nanostructures.

In the model systems of the resonant tunneling diode and the superlattice, the first step was to analyse the complex and chaotic spatiotemporal oscillatory scenarios, which occur through competing spatial and temporal instabilities. Patterns should then be selected through a time delayed feedback loop of the output signal. Thereby, methods of time delayed feedback control (Autosynchronization) which allow the stabilization of unstable periodic orbits should be applied to spatiotemporal patterns.