Hopping conduction in a "superlattice"

We have used the formulation for the "Stark ladder," and a two-well model to describe hopping conduction via acoustical phonons in a "superlattice." Results show that negative differential conductance may occur when the "Stark-ladder" energy eFd is greater than the energy bandwidth. The mechanism is due to the fact that the transition probability at high fields decreases with the increase of F, because the electronic wave functions become more localized. © 1975 The American Physical Society.