THE INFLUENCE OF IMPERFECTIONS AND WEAK DISORDER ON DOMAIN FORMATION IN SUPERLATTICES

The influence of imperfections and weak disorder on the vertical charg e transport in semiconductor superlattices at high electric fields is investigated. We present numerical simulations of the stable high-fiel d domain states and of the self-generated spatio-temporal current osci llations, and demonstrate that the current-voltage characteristics in the regime of domain formation are extremely sensitive to small amount s of disorder introduced by fluctuations of the well and barrier width s as well as the doping densities in the growth direction. Comparison with experiment shows that such fluctuations can explain the irregular ity of the current branches observed in the measured characteristics. It is possible to identify the location of a single imperfection withi n the superlattice structure from the calculated current-voltage chara cteristics. Disorder also strongly affects the regime in which oscilla tory current instabilities occur as well as the frequency and the mode of the oscillations. We propose to use these investigations as a nove l method to detect growth-related imperfections in a superlattice.