Coulomb Blockade Observed in InAs/AlGaSb Nanostructures Produced by an Atomic Force Microscope Oxidation Process

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Abstract
We fabricated and characterized an InAs/AlGaSb single electron transistor produced by the atomic force microscope (AFM) oxidation process. The structure of the transistor we developed has two in-plane gate electrodes which are separated from the current channel by a 0.1-µm-wide gap defined by AFM oxidation and selective GaSb/AlGaSb and InAs etching processes. A complete transistor operation, including clear pinch-off characteristics is achieved by applying negative gate voltages at 4.2 K. Near the pinch-off, an island is formed in the middle of the InAs channel by depleting narrow InAs constrictions fabricated on both sides of the island. We observed a Coulomb gap of 1.6 mV, which is consistent with the estimated self-capacitance of the island. The oscillatory behavior in the I–V characteristics suggests a contribution of quantum effects to the electron tunneling process.