Current self-oscillations in semiconductors with a region of negative differential resistivity in their current-field characteristic are known since J. B. Gunn’s early experiments on n-GaAs samples in 1963. Most studied are Gunn self- oscillations in one-dimensional spatial configurations which appear when planar contacts are placed in bulk semiconductor samples: during each period of the current oscillation, a charge dipole wave is triggered at the injecting contact, moves and is annihilated at the receiving contact. Dynamics of planar dipole waves can be surprisingly rich for systems with one-dimensional geometry: besides periodic self- oscillations, under dc voltage bias there may appear period doubling, frequency blocking and intermittency routes to (low-dimensional) chaos.