SCATTERING RATES OF WANNIER STATES IN SUPERLATTICES IN AN ELECTRIC-FIELD

The scattering rates of Wannier states in superlattices in an electric field by acoustic phonons, optical phonons, ionized impurities, and interface roughness are calculated. The explicit analytical expressions are given, and the results calculated for a typical superlattice structure are discussed. As the electric field increases, the scattering rates by acoustic and optical phonons increase first, reach a maximum, and then decrease rapidly. They form the main mechanism of negative differential conduction in the hopping-conduction framework. The critical field, at which the scattering rate reaches a maximum, corresponds to that of the potential drop across the superlattice period equal to the width of the miniband. The variations of scattering rates by impurity and interface roughness with electric field differ apparently from that of phonons. © 1994 The American Physical Society.