Two-dimensional oscillatory patterns in semiconductors with point contacts

Planar samples of n-GaAs with attached point contacts at different dc voltages may display a variety of spatiotemporal patterns arising from the dynamics of curved charge dipole waves. Patterns rank from oscillations due to recycling and motion of simple quasiplanar or cylindrical wave fronts to more complex patterns that include merging and splitting of different fronts. Results of numerical simulations are interpreted by means of simple one-dimensional asymptotic theories.