Miniband transport in vertical superlattice field-effect transistors

We study the nonequilibrium transport of two-dimensional electrons through a periodic potential. Our samples are fabricated using the cleaved-edge overgrowth technique to provide a vertical field-effect transistor with an undoped GaAs/AlGaAs superlattice channel orthogonal to the current flow. We find a pronounced negative differential resistance, the magnitude of which increases with increasing modulation strength. The data are qualitatively consistent with the Esaki-Tsu transport model in minibands, which we calculate for the given samples. We emphasize the significance of the two-dimensionality of the electron system and the gate to inhibit domain formation. Weak features in the source-drain current are attributed to Bloch-phonon resonances.