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Strain and Charge Transport in InAsP-InP and InP-InAs Core-Shell Nanowires

Göransson, David LU (2019)
Abstract
The mechanical, optical, and electrical properties of III-V semiconductor heterostructures are investigated in this
thesis. The semiconductor materials are grown by metal-organic vapor phase epitaxy, yielding wire shaped crystals
(nanowires) having a length of ~ 1 μm and diameter of ~ 100 nm. Nanowires are relevant for many applications,
such as optical detectors, photovoltaics, light emitting diodes, and transistors. Nanowires are also used in the field
of quantum devices, for the study of quantum dots and Josephson junctions.
In this thesis, InAsP-InP and InP-InAs core-shell nanowires of wurtzite crystal phase are investigated. The InAsP
nanowires are grown epitaxially by the method of Au particle assisted... (More)
The mechanical, optical, and electrical properties of III-V semiconductor heterostructures are investigated in this
thesis. The semiconductor materials are grown by metal-organic vapor phase epitaxy, yielding wire shaped crystals
(nanowires) having a length of ~ 1 μm and diameter of ~ 100 nm. Nanowires are relevant for many applications,
such as optical detectors, photovoltaics, light emitting diodes, and transistors. Nanowires are also used in the field
of quantum devices, for the study of quantum dots and Josephson junctions.
In this thesis, InAsP-InP and InP-InAs core-shell nanowires of wurtzite crystal phase are investigated. The InAsP
nanowires are grown epitaxially by the method of Au particle assisted vapor-liquid-solid growth. They are then
covered by an InP surface layer to obtain InAsP-InP core-shell nanowires. The mechanical strain is measured in the
core-shell nanowires by use of X-ray diffraction. The atomic plane spacing is obtained and related to the mechanical
strain which originate from the epitaxial interface between core and shell. The strain is found to be oriented mainly
along the axis of the nanowires. This axial strain is shown to increase with the thickness of the InP shell layer. This
increase of strain is also found in measurements of the bandgap of the InAsP cores in the core-shell nanowires.

The growth method selective area epitaxy is applied to produce pure wurtzite crystal phase InP-InAs core-shell nanowires.The InAs shell exhibit triangular cross section and the InP core has hexagonal cross section. The chargecarrier accumulation in the InAs shell enables the formation of a quantum structure that produce conducting
channels located along the corners of the triangular shell. The electrical transport through the InAs shell is
investigated at temperatures < 1 K. The nanowires are first probed by Coulomb blockade transport. A method with
four contact electrodes connected to the InAs shell is used to investigate the directional dependence of the Coulomb
blockade, demonstrating that the corners of the shell are highly coupled and that electrons are delocalized over the
full shell volume. Next, transport measurements with low resistance superconducting contacts show induced
superconductivity. A gate tunable supercurrent is produced and a directional dependence of the conductance is
found in the InAs shell. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Schäpers, Thomas, Peter Grünberg Institut, Forschungszentrum Jülich, Germany
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Nanowire, InAsP-InP core-shell nanowire, InP-InAs core-shell nanowire, strain, XRD, charge transport, Coulomb blockade, Josephson junction, Fysicumarkivet A:2019:Göransson
pages
98 pages
publisher
Department of Physics, Lund University
defense location
Rydbergsalen, Fysicum, Sölvegatan 14, Lund University, Faculty of Engineering LTH
defense date
2019-04-29 09:15:00
ISBN
978-91-7895-056-0
978-91-7895-057-7
language
English
LU publication?
yes
id
efc44c26-6882-4ca5-8e4b-6151d759d2b8
date added to LUP
2019-04-01 17:11:17
date last changed
2022-04-27 13:48:00
@phdthesis{efc44c26-6882-4ca5-8e4b-6151d759d2b8,
  abstract     = {{The mechanical, optical, and electrical properties of III-V semiconductor heterostructures are investigated in this<br/>thesis. The semiconductor materials are grown by metal-organic vapor phase epitaxy, yielding wire shaped crystals<br/>(nanowires) having a length of ~ 1 μm and diameter of ~ 100 nm. Nanowires are relevant for many applications,<br/>such as optical detectors, photovoltaics, light emitting diodes, and transistors. Nanowires are also used in the field<br/>of quantum devices, for the study of quantum dots and Josephson junctions.<br/>In this thesis, InAsP-InP and InP-InAs core-shell nanowires of wurtzite crystal phase are investigated. The InAsP<br/>nanowires are grown epitaxially by the method of Au particle assisted vapor-liquid-solid growth. They are then<br/>covered by an InP surface layer to obtain InAsP-InP core-shell nanowires. The mechanical strain is measured in the<br/>core-shell nanowires by use of X-ray diffraction. The atomic plane spacing is obtained and related to the mechanical<br/>strain which originate from the epitaxial interface between core and shell. The strain is found to be oriented mainly<br/>along the axis of the nanowires. This axial strain is shown to increase with the thickness of the InP shell layer. This<br/>increase of strain is also found in measurements of the bandgap of the InAsP cores in the core-shell nanowires.<br/><br/>The growth method selective area epitaxy is applied to produce pure wurtzite crystal phase InP-InAs core-shell nanowires.The InAs shell exhibit triangular cross section and the InP core has hexagonal cross section. The chargecarrier accumulation in the InAs shell enables the formation of a quantum structure that produce conducting<br/>channels located along the corners of the triangular shell. The electrical transport through the InAs shell is<br/>investigated at temperatures &lt; 1 K. The nanowires are first probed by Coulomb blockade transport. A method with<br/>four contact electrodes connected to the InAs shell is used to investigate the directional dependence of the Coulomb<br/>blockade, demonstrating that the corners of the shell are highly coupled and that electrons are delocalized over the<br/>full shell volume. Next, transport measurements with low resistance superconducting contacts show induced<br/>superconductivity. A gate tunable supercurrent is produced and a directional dependence of the conductance is<br/>found in the InAs shell.}},
  author       = {{Göransson, David}},
  isbn         = {{978-91-7895-056-0}},
  keywords     = {{Nanowire; InAsP-InP core-shell nanowire; InP-InAs core-shell nanowire; strain; XRD; charge transport; Coulomb blockade; Josephson junction; Fysicumarkivet A:2019:Göransson}},
  language     = {{eng}},
  month        = {{04}},
  publisher    = {{Department of Physics, Lund University}},
  school       = {{Lund University}},
  title        = {{Strain and Charge Transport in InAsP-InP and InP-InAs Core-Shell Nanowires}},
  url          = {{https://lup.lub.lu.se/search/files/62518747/Strain_and_Charge_Transport_in_InAsP_InP_and_InAs_InP_Core_Shell_Nanowires_Doctoral_Thesis_David_G_ransson.pdf}},
  year         = {{2019}},
}