Observation Of Quantized Conductance Research Articles

Observation of quantized conductance in split-gate In0.53Ga0.47As/In0.77Ga0.23As/InP point contacts using Cr/Au p-InP Schottky barriers

We report on the observation of quantized conductance in split-gate In0.53Ga0.43As/Ga0.77In0.23As/InP point contacts. For the Schottky gates Au/Cr in combination with p-InP was used. As a result our split-gate point contacts show low pinch-off voltages and no measurable leakage current through the gates. Up to five conductance steps were observed at a temperature of 1.4 K. Our approach to fabricate split-gate Schottky contacts can be used for quantum point contacts operating at higher temperatures as well as for superconductive quantum point contacts.

Quantized conductance in a heterostructurally defined Ga0.25In0.75As/InP quantum wire

We report on the observation of quantized conductance up to 10 K in epitaxially regrown, heterostructurally defined, 100-nm-wide Ga0.25In0.75As/InP quantum wires. In addition to the plateaus at integer steps of 2e2/h, we observe plateaus at 0.2(2e2/h), 0.7(2e2/h), and 1.5(2e2/h), indicating spin polarization at zero magnetic field. Of these, the first two plateaus appear to evolve into one at around 0.5(2e2/h) when the sample is subjected to a magnetic field parallel to the quantum wire. The observation of quantized conductance is made possible by the substantial improvement in the quality of the interface by regrowth.

Studies of confined states and quantum size effects with scanning tunneling microscopy

Scanning tunneling microscopy (STM) provides new ways for studying electron confinement and quantum size effects and expands the range of materials and conditions under which such effects can be observed. Here we discuss three applications: (a) The confinement of electrons in metal surface states by surface steps or by corrals fabricated using single atoms, and the imaging of the probability amplitudes of the resulting confined states; (b) the detection of electron states involving confinement between the surface layer and sub-surface interfaces; (c) the observation of quantized conductance at room temperature using metal structures formed by the STM tip.