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Electronic, Transport, and Optical Properties of Broken-Gap Heterostructures

Nilsson, Karin LU (2007)
Abstract (Swedish)
Popular Abstract in Swedish

I avhandlingen undersöks fysikaliska egenskaper hos heterostrukturer med brutna energigap med hjälp av en flerbands k.p modell och självkonsistenta beräkningar.



Heterostrukturer med brutna energigap består av halvledarna InAs, GaSb och AlSb och



karaktäriseras av en speciell bandstruktur där ledningsbandet i InAs överlappar med valensbandet i GaSb. På grund av bandöverlappet uppkommer antikorsningsområden i energidispersionen samt elektron-hål hybridisering.



Förutom en populärvetenskaplig sammanfattning på svenska och en inledning består avhandlingen av sju vetenskapliga artiklar. Artikel 1 sammanfattar tidigare forskning kring... (More)
Popular Abstract in Swedish

I avhandlingen undersöks fysikaliska egenskaper hos heterostrukturer med brutna energigap med hjälp av en flerbands k.p modell och självkonsistenta beräkningar.



Heterostrukturer med brutna energigap består av halvledarna InAs, GaSb och AlSb och



karaktäriseras av en speciell bandstruktur där ledningsbandet i InAs överlappar med valensbandet i GaSb. På grund av bandöverlappet uppkommer antikorsningsområden i energidispersionen samt elektron-hål hybridisering.



Förutom en populärvetenskaplig sammanfattning på svenska och en inledning består avhandlingen av sju vetenskapliga artiklar. Artikel 1 sammanfattar tidigare forskning kring heterostrukturer med brutna energigap medan de övriga artiklarna innehåller ny kunskap om dessa material.



Interbandtransport i tunnlingsstrukturer undersöks i artiklarna 2, 3 och 6.



I artikel 2 demonstreras vikten av att inkludera både de spänningar som uppkommer på grund av att halvledarnas gitter inte passar ihop och bulk anisotropin i den teoretiska modellen. I artikel 3 studeras den elektriska strömmens spinpolarisering i närvaro av ett kvantiserande magnetiskt fält. Spinpolarisering kan vara betydande vilket gör dessa system lämpliga som att användas som spinfilter. I artikel 6 undersöks spänningströskeln. Artikeln föreslår att ett magnetiskt fält kan användas för att ändra transportegenskaperna mellan tunnlingsbeteendet och ett ohmskt beteende.



I artikel 4 undersöks spinpolariseringen hos en elektron-hål gas i en asymmetrisk kvantbrunn under en lateral likström. Spinpolariseringens tecken ändras vid övergången mellan normal och hybridiserad halvledare.



I artikel 5 undersöks hur cyklotronmassan och g-faktorn för hybridiserade egentillstånd i en kvantbrunn beror på det magnetiska fältet. Vid antikorsningarna uppstår karaktäristiska diskontinuiteter och g-faktorns tecken kan ändras.



I artikel 7 undersöks optiska övergångar inducerade av linjärpolariserat ljus. Artikeln visar hur den lägre symmetrin vid gränsytorna, bulk inversionssymmetrin och elektron-hål hybridiseringen gör att fler optiska övergångar blir tillåtna. (Less)
Abstract
This thesis examines the physical properties of broken-gap heterostructures using a multiband k.p model and self-consistent calculations. Broken-gap heterostructures, made from InAs, GaSb, and AlSb, are characterized by a special band alignment with an overlap between the InAs conduction band and the GaSb valence band. The band overlap results in anticrossing regions in the energy dispersions and hybridization of electrons and holes.



After a summary in Swedish, intended for the general public, and an introduction, seven original papers follow. Paper 1 reviews the understanding of broken-gap heterostructures prior to this thesis. Papers 2-7 improve and extend this understanding by considering different physical properties... (More)
This thesis examines the physical properties of broken-gap heterostructures using a multiband k.p model and self-consistent calculations. Broken-gap heterostructures, made from InAs, GaSb, and AlSb, are characterized by a special band alignment with an overlap between the InAs conduction band and the GaSb valence band. The band overlap results in anticrossing regions in the energy dispersions and hybridization of electrons and holes.



After a summary in Swedish, intended for the general public, and an introduction, seven original papers follow. Paper 1 reviews the understanding of broken-gap heterostructures prior to this thesis. Papers 2-7 improve and extend this understanding by considering different physical properties and by using more sophisticated models.



Paper 2 demonstrates the importance of lattice-mismatch-induced strain and bulk anisotropy on interband transport in tunneling structures. The choice of substrate not only alters the number of peaks in the transmission spectra, but also affects the current-density magnitude.



Paper 3 considers interband tunneling under a quantizing magnetic field. The spin polarization of the tunneling current can be considerable, making these structures possible spin filters.



In Paper 4, a spin polarization of the electron-hole gas in an asymmetric quantum well is generated by a lateral dc current. The sign of the spin polarization, determined by the layer widths, change as the system changes from a normal semiconductor to a hybridized semiconductor.



Paper 5 considers the magnetic-field-dependence of cyclotron masses and g-factors of hybridized quantum-well eigenstates. Characteristic discontinuities appear at the anticrossings where also the g-factor's sign can change.



Paper 6 also considers interband transport, but focuses on the bias threshold. It is proposed that the strength of a magnetic field can tune the transport between an Ohmic and a resonant-tunneling behavior.



Paper 7 considers optical transitions induced by linearly polarized light. The reduced crystal symmetry at the interfaces, the bulk inversion asymmetry, and the electron-hole hybridization allow additional optical transitions between the quantum-well subbands. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Dr. Ekenberg, Ulf, Mikroteknik och tillämpad fysik, Institutionen för mikroelektronik och informationsteknik, KTH, Stoc
organization
publishing date
type
Thesis
publication status
published
subject
keywords
relaxation, magnetic resonance, supraconductors, magnetic and optical properties, k.p calculations, Condensed matter:electronic structure, electrical, interband transport, electron-hole hybridization, spin polarization, spectroscopy, spektroskopi, Kondenserade materiens egenskaper:elektronstruktur, egenskaper (elektriska, magnetiska och optiska), supraledare, magnetisk resonans
pages
209 pages
publisher
Solid State Theory, Physics Department, Lund University, Sölvegatan 14A, S-223 62 Lund, Sweden
defense location
Lecture hall B, Physics Department, Sölvegatan 14A, Lund
defense date
2007-03-16 13:15
ISBN
978-91-628-7081-2
language
English
LU publication?
yes
id
8a7e8f3b-bc73-4ca0-b6a9-b00e72184aca (old id 548192)
date added to LUP
2007-09-28 12:33:41
date last changed
2016-09-19 08:45:12
@misc{8a7e8f3b-bc73-4ca0-b6a9-b00e72184aca,
  abstract     = {This thesis examines the physical properties of broken-gap heterostructures using a multiband k.p model and self-consistent calculations. Broken-gap heterostructures, made from InAs, GaSb, and AlSb, are characterized by a special band alignment with an overlap between the InAs conduction band and the GaSb valence band. The band overlap results in anticrossing regions in the energy dispersions and hybridization of electrons and holes.<br/><br>
<br/><br>
After a summary in Swedish, intended for the general public, and an introduction, seven original papers follow. Paper 1 reviews the understanding of broken-gap heterostructures prior to this thesis. Papers 2-7 improve and extend this understanding by considering different physical properties and by using more sophisticated models.<br/><br>
<br/><br>
Paper 2 demonstrates the importance of lattice-mismatch-induced strain and bulk anisotropy on interband transport in tunneling structures. The choice of substrate not only alters the number of peaks in the transmission spectra, but also affects the current-density magnitude.<br/><br>
<br/><br>
Paper 3 considers interband tunneling under a quantizing magnetic field. The spin polarization of the tunneling current can be considerable, making these structures possible spin filters.<br/><br>
<br/><br>
In Paper 4, a spin polarization of the electron-hole gas in an asymmetric quantum well is generated by a lateral dc current. The sign of the spin polarization, determined by the layer widths, change as the system changes from a normal semiconductor to a hybridized semiconductor.<br/><br>
<br/><br>
Paper 5 considers the magnetic-field-dependence of cyclotron masses and g-factors of hybridized quantum-well eigenstates. Characteristic discontinuities appear at the anticrossings where also the g-factor's sign can change.<br/><br>
<br/><br>
Paper 6 also considers interband transport, but focuses on the bias threshold. It is proposed that the strength of a magnetic field can tune the transport between an Ohmic and a resonant-tunneling behavior.<br/><br>
<br/><br>
Paper 7 considers optical transitions induced by linearly polarized light. The reduced crystal symmetry at the interfaces, the bulk inversion asymmetry, and the electron-hole hybridization allow additional optical transitions between the quantum-well subbands.},
  author       = {Nilsson, Karin},
  isbn         = {978-91-628-7081-2},
  keyword      = {relaxation,magnetic resonance,supraconductors,magnetic and optical properties,k.p calculations,Condensed matter:electronic structure,electrical,interband transport,electron-hole hybridization,spin polarization,spectroscopy,spektroskopi,Kondenserade materiens egenskaper:elektronstruktur,egenskaper (elektriska,magnetiska och optiska),supraledare,magnetisk resonans},
  language     = {eng},
  pages        = {209},
  publisher    = {ARRAY(0x90288c0)},
  title        = {Electronic, Transport, and Optical Properties of Broken-Gap Heterostructures},
  year         = {2007},
}