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Giant electron-hole transport asymmetry in ultra-short quantum transistors.

Nat Commun. 2017 05 31;8:15491

Authors: McRae AC, Tayari V, Porter JM, Champagne AR

Abstract

Making use of bipolar transport in single-wall carbon nanotube quantum transistors would permit a single device to operate as both a quantum dot and a ballistic conductor or as two quantum dots with different charging energies. Here we report ultra-clean 10 to 100?nm scale suspended nanotube transistors with a large electron-hole transport asymmetry. The devices consist of naked nanotube channels contacted with sections of tube under annealed gold. The annealed gold acts as an n-doping top gate, allowing coherent quantum transport, and can create nanometre-sharp barriers. These tunnel barriers define a single quantum dot whose charging energies to add an electron or a hole are vastly different (e-h charging energy asymmetry). We parameterize the e-h transport asymmetry by the ratio of the hole and electron charging energies ?e-h. This asymmetry is maximized for short channels and small band gap tubes. In a small band gap device, we demonstrate the fabrication of a dual functionality quantum device acting as a quantum dot for holes and a much longer quantum bus for electrons. In a 14?nm-long channel, ?e-h reaches up to 2.6 for a device with a band gap of 270?meV. The charging energies in this device exceed 100?meV.

PMID: 28561024 [PubMed]