Transport in Novel Gated Quantum Wires: The Impact of Wire Length

Split-gate quantum wires of various lengths including 0.0 µm (constrictions), 0.5 µm, and 1.0 µm have been fabricated on an AlGaAs/GaAs modulation-doped heterostructure. Confinement is achieved using a split-gate formed by two 40 nm Au/Pd lines, resulting in small gate leakage and short electron-beam writing times. In a two-probe measurement, we have observed strong conductance steps at 4.2 K in 0.5 µm long split-gate quantum wires. These features, which are characteristic of near ballistic electron transport through the wire, are present at temperatures as high as 10 K. Transport through the 0.0 µm constrictions was dominated by tunneling and transport in the 1.0 µm long wires was of a diffusive nature.