Nonlinear Electron Transport in an Asymmetric Microjunction: A Ballistic Rectifier

An asymmetric artificial scatterer in a semiconductor microjunction is shown to dramatically affect the nonlinear transport of ballistic electrons. The chosen device geometry, defined in a GaAs-AlGaAs heterostructure, successfully guides carriers in a predetermined spatial direction, independent of the direction of the input current $I$. From the nonlinear current-voltage characteristic we obtain unusual symmetry relations for the four-terminal resistances with ${R}_{ij,kl}(I)\ensuremath{\approx}{\ensuremath{-}R}_{ij,kl}(\ensuremath{-}I)$ and ${R}_{ij,kl}(B)\ensuremath{\gg}{R}_{kl,ij}(\ensuremath{-}B)$ even at zero magnetic field $B$. The ballistic rectifier thus realized relies on a new kind of rectification mechanism entirely different from that of an ordinary diode.