Quantum Transport in Heterostructure Nanowire Devices

Bahram Ganjipour

Research output: ThesisDoctoral Thesis (compilation)


This thesis investigates electronic transport in several types of novel heterostructure nanowires. The first part of the thesis focuses on band-to-band mechanisms in heterostructure nanowires for low-power electronics. First, tunnel field-effect transistors (TFETs) based on InP/GaAs heterostructure nanowires with n-i-p doping profile are explored. To further enhance the interband tunneling current, we study the broken-gap alignment GaSb/InAsSb heterostructure that allows for high-efficiency interband tunneling. The materials system is first investigated as an Esaki diode with different doping profiles to study the effect of doping on the diode characteristics. The nanowires are then processed into TFETs by fabricating omega-shaped top gates on InAsSb segments. The final part of this study is a demonstration of the InP/InGaAs core/shell nanowire Esaki tunnel diodes with different InGaAs shell doping concentrations for tandem solar cell applications. The results show the versatility of III–V heterostructure nanowires for future energy-efficient electronic devices.
The second part of this thesis deals with experimental studies of GaSb/InAsSb core/shell nanowires, correlating growth parameters with nanowire transport properties. The effect of InAsSb shell thickness on the electronic properties of nanowires is systematically investigated. The results show that the thickness of the InAsSb shell has a strong effect on the semiconductor properties. With decreasing shell thickness, nanowires with ambipolar character are found to exhibit a semimetal to semiconductor transition due to increasing confinement in the InAsSb shell. Finally, the nanowires with the ambipolar conduction are used to experimentally demonstrate frequency multiplication.
The final part of this thesis investigates low-temperature hole transport in GaSb and GaSb/InAs core/shell nanowires. We study the magneto-transport properties of confined holes in GaSb/InAs core/shell nanowires. Here, we observe a twofold spin-degeneracy, and the Zeeman splitting of the ground states allows us to extract the g-factor. An energy gap of ΔE = 300 μeV is extracted from an avoided level-crossing that may provide an estimation of the spin–orbit interaction strength in GaSb/InAs core/shell nanowire quantum dots.
Original languageEnglish
Awarding Institution
  • Solid State Physics
  • Thelander, Claes, Supervisor
Award date2014 Jun 13
Print ISBNs978-91-7623-025-1
Publication statusPublished - 2014

Bibliographical note

Defence details

Date: 2014-06-13
Time: 09:30
Place: Lecture hall Rydbergsalen, Department of Physics, Sölvegatan 14, Lund University Faculty of Engineering

External reviewer(s)

Name: Franceschi, Silvano De
Title: Dr
Affiliation: CEA Grenoble, France


Subject classification (UKÄ)

  • Condensed Matter Physics


  • Fysicumarkivet A:2014:Ganjipour


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