Dynamics of electric field domain walls in semiconductor superlattices

A self-consistent microscopic model of sequential tunneling in superlattices is employed to investigate self-sustained current oscillations. Current spikes – high-frequency modulation due to well-to-well hopping of charge monopole domain walls – are naturally reproduced. Moreover, as the contact doping shrinks, the recycling and motion of charge dipoles resulting in a lower-frequency oscillatory mode is predicted. For low contact doping, this mode dominates and monopole oscillations disappear. At intermediate doping, hysteresis between both the oscillatory modes may be possible.