High-field transport in semiconductor superlattices for interacting   Wannier-Stark levels
  We develop a microscopic theory of electron transport in superlattices within the Wannier-Stark approach by including the interaction associated with Zener tuneling among the energy levels pertaining to adjacent quantum wells. By using a Monte Carlo technique we have simulated the hopping motion associated with absorption and emission of polar optical phonons and determined the main transport parameters for the case of a GaAs/GaAlAs structure at room temperature. The interaction among the levels is found to be responsible for a systematic increase of the level energy with respect to the bottom of the quantum well at electric fields above about 20 kV/cm. When compared with the non-interacting case, at the highest fields the average carrier energy evidences a consistent increase which leads to a significant softening of the negative differential value of both the drift velocity and diffusivity. 
Angelo Guida, Lino Reggiani and Marcello Rosini