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Scanning Tunneling Microscopy Induced Luminescence Studies of Semiconductor Nanostructures

Håkanson, Ulf LU (2003)
Abstract
This thesis treats scanning tunneling luminescence (STL) investigations of semiconductor nanostructures. The STL technique combines scanning tunneling microscopy (STM) with detection of photons, induced by the tunneling electrons. The high spatial resolution in STM and the local excitation allow for optical investigations on the nanometer-scale.



The work concerns design and implementation of an optical detection system used for STL studies of single InP quantum dots (QDs) overgrown with thin layers of GaInP. Constant current imaging together with STL spectra and monochromatic photon mapping were used to correlate the surface topography with the optical properties of the QDs. It was found that the QDs act as seeds for the... (More)
This thesis treats scanning tunneling luminescence (STL) investigations of semiconductor nanostructures. The STL technique combines scanning tunneling microscopy (STM) with detection of photons, induced by the tunneling electrons. The high spatial resolution in STM and the local excitation allow for optical investigations on the nanometer-scale.



The work concerns design and implementation of an optical detection system used for STL studies of single InP quantum dots (QDs) overgrown with thin layers of GaInP. Constant current imaging together with STL spectra and monochromatic photon mapping were used to correlate the surface topography with the optical properties of the QDs. It was found that the QDs act as seeds for the GaInP overgrowth, where elongated GaInP islands are formed. The emission from single QDs was observed to be shifted towards higher energies with increasing cap layer thickness, which by multi-band k.p theory was determined to be induced by strain. The geometry of the overgrowth was realistically modelled in the calculations, using data from STM and transmission electron microscopy. Theoretical emission energies were also calculated, which are in good agreement with the experimental results.



Studies of the GaInP islands showed that the InP QDs locally induce domains in the islands with high degree of ordering in the GaInP. The emission from these domains was found to occur at an energy below the emission from the GaInP barrier material. High polarization anisotropy for the island luminescence was observed by photoluminescence measurements, in which maximum emission intensity was detected for light polarized parallel to the elongation of the islands. (Less)
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author
opponent
  • Professor Weber, Eicke, Department of Materials Science and Engineering, University of California, Berkeley, USA
organization
publishing date
type
Thesis
publication status
published
subject
keywords
transmission electron microscopy (TEM), III-V semiconductors, low-dimensional structures, nanostructures, single dot spectroscopy, Stranski-Krastanow, quantum dot (QD), Semiconductory physics, polarization, ordering, InP, GaInP, photon mapping, scanning tunneling microscopy (STM), scanning tunneling luminescence (STL), Halvledarfysik, Fysicumarkivet A:2003:Håkanson
pages
110 pages
publisher
Division of Solid State Physics, Department of Physics, Lund University, Box 118, SE-221 00 Lund, Sweden,
defense location
Lecture Hall B, Department of Physics, Lund Institute of Technology
defense date
2003-05-16 10:15
external identifiers
  • Other:LUFTD2/TFFF-0065
ISBN
91-628-5596-4
language
English
LU publication?
yes
id
6ae9f3b6-6f88-4d44-81ae-5cc7e5835fca (old id 465789)
date added to LUP
2007-09-28 09:59:59
date last changed
2016-09-19 08:45:06
@misc{6ae9f3b6-6f88-4d44-81ae-5cc7e5835fca,
  abstract     = {This thesis treats scanning tunneling luminescence (STL) investigations of semiconductor nanostructures. The STL technique combines scanning tunneling microscopy (STM) with detection of photons, induced by the tunneling electrons. The high spatial resolution in STM and the local excitation allow for optical investigations on the nanometer-scale.<br/><br>
<br/><br>
The work concerns design and implementation of an optical detection system used for STL studies of single InP quantum dots (QDs) overgrown with thin layers of GaInP. Constant current imaging together with STL spectra and monochromatic photon mapping were used to correlate the surface topography with the optical properties of the QDs. It was found that the QDs act as seeds for the GaInP overgrowth, where elongated GaInP islands are formed. The emission from single QDs was observed to be shifted towards higher energies with increasing cap layer thickness, which by multi-band k.p theory was determined to be induced by strain. The geometry of the overgrowth was realistically modelled in the calculations, using data from STM and transmission electron microscopy. Theoretical emission energies were also calculated, which are in good agreement with the experimental results.<br/><br>
<br/><br>
Studies of the GaInP islands showed that the InP QDs locally induce domains in the islands with high degree of ordering in the GaInP. The emission from these domains was found to occur at an energy below the emission from the GaInP barrier material. High polarization anisotropy for the island luminescence was observed by photoluminescence measurements, in which maximum emission intensity was detected for light polarized parallel to the elongation of the islands.},
  author       = {Håkanson, Ulf},
  isbn         = {91-628-5596-4},
  keyword      = {transmission electron microscopy (TEM),III-V semiconductors,low-dimensional structures,nanostructures,single dot spectroscopy,Stranski-Krastanow,quantum dot (QD),Semiconductory physics,polarization,ordering,InP,GaInP,photon mapping,scanning tunneling microscopy (STM),scanning tunneling luminescence (STL),Halvledarfysik,Fysicumarkivet A:2003:Håkanson},
  language     = {eng},
  pages        = {110},
  publisher    = {ARRAY(0x7854208)},
  title        = {Scanning Tunneling Microscopy Induced Luminescence Studies of Semiconductor Nanostructures},
  year         = {2003},
}