Zener antiresonance in the quantum diffusion of semiconductor superlattices

The well-known theory of quantum transport is extended to an approach that allows the description of quantum diffusion in strongly biased multi-band semiconductors and semiconductor superlattices. The longitudinal diffusion coefficient is identified and expressed by a quantity that satisfies a different quantum-kinetic equation than the carrier distribution function, from which the drift velocity is calculated. Results are obtained for a simple two-band model at the interband (intersubband) tunnelling resonance. In contrast to the drift velocity, the diffusion coefficient may exhibit a Zener antiresonance.