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Resonant Tunneling in Laterally Confined Quantum Structures

Gustafson, Boel LU (2001)
Abstract
In the thesis, three-dimensionally confined resonant tunneling structures were studied experimentally. Two approaches were used for obtaining quantum confinement: gate-defined lateral constriction of double barrier structures, and epitaxial growth of self-assembled quantum dots. In addition, the thesis deals with the basic development of large-area double barrier resonant tunneling diodes, as a starting point for more advanced quantum dot structures.



Large area double barrier resonant tunneling diodes in several material systems were investigated: GaAs/Ga0.5In0.5P, GaAs/GaAs0.2P0.8, GaAs/GaP, and Ga0.5In0.5As/InP. Emphasis was placed on GaInP/GaAs structures, which were optimized in terms of well width and of doping... (More)
In the thesis, three-dimensionally confined resonant tunneling structures were studied experimentally. Two approaches were used for obtaining quantum confinement: gate-defined lateral constriction of double barrier structures, and epitaxial growth of self-assembled quantum dots. In addition, the thesis deals with the basic development of large-area double barrier resonant tunneling diodes, as a starting point for more advanced quantum dot structures.



Large area double barrier resonant tunneling diodes in several material systems were investigated: GaAs/Ga0.5In0.5P, GaAs/GaAs0.2P0.8, GaAs/GaP, and Ga0.5In0.5As/InP. Emphasis was placed on GaInP/GaAs structures, which were optimized in terms of well width and of doping concentration.



Gate-defined lateral confinement was achieved by a buried metal gate positioned 30 nm above a GaInP/GaAs double barrier. The Schottky depletion from the metal directs the current to a designed opening in the gate. The opening constitutes a conducting channel through the depleted semiconductor, where an applied gate voltage alters the effective width of the channel. Room-temperature transistor action was measured in structures with large opening area, and multiple current peaks in the low-temperature current-voltage characteristics of small-area devices indicate that lateral quantum confinement was achieved. The gate and magnetic-field dependence of the features obtained showed qualitative agreement with calculations performed on a coupled 1D-0D-1D quantum system.



Low-temperature electron transport through self-assembled InAs dots in InP barriers showed several distinct current peaks. Utilizing As/P exchange reactions on the InP surface, extremely low dot densities (N=4e6 cm-2) was achieved, corresponding to approximately 150 quantum dots in a macroscopic mesa structure. Transport through single- and double-dot layers have been investigated. In the stacked samples, a peak-to-valley ratio of 85 was obtained. (Less)
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author
opponent
  • Dr Seabaugh, Alan, University of Notre Dame
organization
publishing date
type
Thesis
publication status
published
subject
keywords
gravitation, relativity, quantum mechanics, classical mechanics, Mathematical and general theoretical physics, Fysik, Physics, High peak-to-valley ratio, Lateral confinement, Quantum dots, Resonant tunneling, Self-assembled quantum dots, Schottky depletion, Buried metal gate, Electron transport, Magnetic-field dependence, Energy level width, Tunneling transistors, Mode coupling, statistical physics, thermodynamics, Matematisk och allmän teoretisk fysik, klassisk mekanik, kvantmekanik, relativitet, statistisk fysik, termodynamik, Technological sciences, Teknik, Fysicumarkivet A:2001:Gustafson
pages
106 pages
publisher
Division of Solid State Physics, Department of Physics, Lund University,Box 118, SE-221 00 Lund, Sweden,
defense location
Sal B Department of Physics
defense date
2001-05-04 10:15
external identifiers
  • Other:ISRN: LUFTD2/TFFF--01/0059--SE
ISBN
91-7874-123-8
language
English
LU publication?
yes
id
43402fe6-e9c9-4d9d-9e99-dcd2954e3610 (old id 41579)
date added to LUP
2007-06-21 12:54:41
date last changed
2016-09-19 08:45:06
@misc{43402fe6-e9c9-4d9d-9e99-dcd2954e3610,
  abstract     = {In the thesis, three-dimensionally confined resonant tunneling structures were studied experimentally. Two approaches were used for obtaining quantum confinement: gate-defined lateral constriction of double barrier structures, and epitaxial growth of self-assembled quantum dots. In addition, the thesis deals with the basic development of large-area double barrier resonant tunneling diodes, as a starting point for more advanced quantum dot structures.<br/><br>
<br/><br>
Large area double barrier resonant tunneling diodes in several material systems were investigated: GaAs/Ga0.5In0.5P, GaAs/GaAs0.2P0.8, GaAs/GaP, and Ga0.5In0.5As/InP. Emphasis was placed on GaInP/GaAs structures, which were optimized in terms of well width and of doping concentration.<br/><br>
<br/><br>
Gate-defined lateral confinement was achieved by a buried metal gate positioned 30 nm above a GaInP/GaAs double barrier. The Schottky depletion from the metal directs the current to a designed opening in the gate. The opening constitutes a conducting channel through the depleted semiconductor, where an applied gate voltage alters the effective width of the channel. Room-temperature transistor action was measured in structures with large opening area, and multiple current peaks in the low-temperature current-voltage characteristics of small-area devices indicate that lateral quantum confinement was achieved. The gate and magnetic-field dependence of the features obtained showed qualitative agreement with calculations performed on a coupled 1D-0D-1D quantum system.<br/><br>
<br/><br>
Low-temperature electron transport through self-assembled InAs dots in InP barriers showed several distinct current peaks. Utilizing As/P exchange reactions on the InP surface, extremely low dot densities (N=4e6 cm-2) was achieved, corresponding to approximately 150 quantum dots in a macroscopic mesa structure. Transport through single- and double-dot layers have been investigated. In the stacked samples, a peak-to-valley ratio of 85 was obtained.},
  author       = {Gustafson, Boel},
  isbn         = {91-7874-123-8},
  keyword      = {gravitation,relativity,quantum mechanics,classical mechanics,Mathematical and general theoretical physics,Fysik,Physics,High peak-to-valley ratio,Lateral confinement,Quantum dots,Resonant tunneling,Self-assembled quantum dots,Schottky depletion,Buried metal gate,Electron transport,Magnetic-field dependence,Energy level width,Tunneling transistors,Mode coupling,statistical physics,thermodynamics,Matematisk och allmän teoretisk fysik,klassisk mekanik,kvantmekanik,relativitet,statistisk fysik,termodynamik,Technological sciences,Teknik,Fysicumarkivet A:2001:Gustafson},
  language     = {eng},
  pages        = {106},
  publisher    = {ARRAY(0xaddc450)},
  title        = {Resonant Tunneling in Laterally Confined Quantum Structures},
  year         = {2001},
}