Negative Differential Mobility and Convective Instability of a Semiconductor Superlattice

Abstract

Although narrow-miniband superlattices have an important transport inhomogeneity manifested in the formation of high-field domains and in periodic structure of the I-V characteristic when the applied voltage increases beyond a threshold,¹ the most interesting transport phenomena in wide-miniband systems are those related to Esaki-Tsu negative differential mobility (NDM) at relatively low electric field.² We report here on a careful examination of the frequency dependence of small-signal ac mobility and the possible fluctuation instability of a planar superlattice subject to negative differential miniband conductance. Our analysis is based on three-dimensional hydrodynamic nonlinear balance equations with accurate microscopic treatment of phonon and impurity scatterings.