Quantum interference in silicon 1D junctionless nanowire field-effect transistors

Schupp, F.J., Mirza, M. M.A. , MacLaren, D. A. , Briggs, G. A. D., Paul, D. J. and Mol, J. A. (2018) Quantum interference in silicon 1D junctionless nanowire field-effect transistors. Physical Review B, 98(23), 235428. (doi: 10.1103/PhysRevB.98.235428)

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We investigate the low-temperature transport in 8 nm diameter Si junctionless nanowire field-eff ect transistors fabricated by top down techniques with a wrap-around gate and two different phosphorus doping concentrations. First we extract the intrinsic gate capacitance of the device geometry from a device that demonstrates Coulomb blockade at 12 mK with over 500 Coulomb peaks across a gate-voltage range of 6 V indicating the formation of an island in the entire 150 nm-long nanowire channel. In two other devices, made from silicon on insulator wafers that were doped to an activated dopant concentration of Si:P 4 x 1019 cm-3 and 2 x 1020 cm-3, we observe quantum interference and use the extracted gate coupling to determine the mean-free paths from the dominant energy scale on the gate-voltage axis. For the higher doped device the analysis yields a mean-free-path of 4 +- 2 nm, which is on the order of the average spacing of phosphorous atoms and suggests scattering on unactivated or activated dopants. For the device with an implanted phosphorous density of 4 x 1019 cm-3 the quantum interference effects suggest a mean-free-path of 10 +- 2 nm, which is comparable to the nanowire width, and thus allows for coherent formation of transversal modes. The results suggest that the low-temperature mobility is limited by scattering on phosphorus dopants rather than the expected surface roughness scattering for nanowires with diameters larger or comparable to the Fermi wavelength. A temperature dependent analysis of Universal Conductance Fluctuations indicates a phase-coherence length greater than the nanowire length for temperatures below 1.9 K and decoherence from 1D electron-electron interactions dominates transport for higher temperatures. Our measurements therefore provide insight into scattering and dephasing mechanisms in technologically relevant silicon device geometries, which will help with future design choices with regards to e.g. doping density.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Mirza, Dr Muhammad M A and MacLaren, Dr Donald and Paul, Professor Douglas
Authors: Schupp, F.J., Mirza, M. M.A., MacLaren, D. A., Briggs, G. A. D., Paul, D. J., and Mol, J. A.
College/School:College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
College of Science and Engineering > School of Physics and Astronomy
Journal Name:Physical Review B
Publisher:American Physical Society
ISSN (Online):2469-9969
Published Online:26 December 2018
Copyright Holders:Copyright © 2018 American Physical Society
First Published:First published in Physical Review B 98(23): 235428
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
503291Molecular-Metal-Oxide-nanoelectronicS (M-MOS): Achieving the Molecular LimitLeroy CroninEngineering and Physical Sciences Research Council (EPSRC)EP/H024107/1CHEM - CHEMISTRY
694301Engineering Quantum Technology Systems on a Silicon PlatformDouglas PaulEngineering and Physical Sciences Research Council (EPSRC)EP/N003225/1ENG - ENGINEERING ELECTRONICS & NANO ENG