We study the nonequilibrium transport of two-dimensional electrons through
a periodic potential. Our samples are fabricated using the cleaved-edge ove
rgrowth technique to provide a vertical field-effect transistor with an und
oped GaAs/AlGaAs superlattice channel orthogonal to the current flow. We fi
nd a pronounced negative differential resistance, the magnitude of which in
creases with increasing modulation strength. The data are qualitatively con
sistent with the Esaki-Tsu transport model in minibands, which we calculate
for the given samples. We emphasize the significance of the two-dimensiona
lity of the electron system and the gate to inhibit domain formation. Weak
features in the source-drain current are attributed to Bloch-phonon resonan
ces. (C) 2001 American Institute of Physics.