Wave dynamics in two-dimensional samples of n-GaAs with point contacts

We present results of numerical simulations of a two-dimensional Kroemer model for the Gunn effect in samples with different number of point contacts. These results can be interpreted with the help of asymptotic theories for particular geometries: a one-dimensional sample and a Corbino disk (a circular sample with a point contact at the center surrounded by a metallic contact attached to its boundary). Comments on open problems and possible experimental verification are also made.