Negative differential conductance in planar one-dimensional/zero-dimensional/one-dimensional GaAs/AlGaAs structures

Abstract

By using high-resolution electron beam lithography and wet etching, we have fabricated semiconducting islands between quantum wires from GaAs/AlGaAs modulation-doped heterostructures. The zero-dimensional islands were realized by displacing a 180 nm section at the center of a 1 μm long and 180 nm wide straight wire in well-controlled steps perpendicular to the wire direction. The narrow connections between the island and the wires introduce potential barriers. Finite bias voltages applied between the source and the drain of the electron waveguide structures permit to observe negative differential conductance, which is interpreted in terms of resonant tunneling of electrons through the barriers. Furthermore, we observe Coulomb blockade oscillations in the differential conductance of the structures.