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Title: Faceting during GaAs quantum dot self-assembly by droplet epitaxy

Abstract

Strain-free GaAs quantum dots (QDs) are grown in a self-assembled fashion by applying Ga droplet epitaxy. The QDs are studied using electron diffraction and atomic force microscopy. Two distinct regimes are observed for the QD shape. QDs whose volume exceeds approximately 3x10{sup 5} Ga atoms are shaped like truncated pyramids with side facets having an angle of about 55 deg. . Smaller QDs are pyramidlike with 25 deg. facets.

Authors:
; ; ; ; ;  [1];  [2]
  1. Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Jungiusstrasse 11, D-20355 Hamburg (Germany)
  2. (Hungary)
Publication Date:
OSTI Identifier:
20971931
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 90; Journal Issue: 20; Other Information: DOI: 10.1063/1.2737123; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ATOMIC FORCE MICROSCOPY; CRYSTAL GROWTH; DROPLETS; ELECTRON DIFFRACTION; GALLIUM ARSENIDES; MOLECULAR BEAM EPITAXY; QUANTUM DOTS; SEMICONDUCTOR MATERIALS

Citation Formats

Heyn, Ch., Stemmann, A., Schramm, A., Welsch, H., Hansen, W., Nemcsics, A., and Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest. Faceting during GaAs quantum dot self-assembly by droplet epitaxy. United States: N. p., 2007. Web. doi:10.1063/1.2737123.
Heyn, Ch., Stemmann, A., Schramm, A., Welsch, H., Hansen, W., Nemcsics, A., & Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest. Faceting during GaAs quantum dot self-assembly by droplet epitaxy. United States. doi:10.1063/1.2737123.
Heyn, Ch., Stemmann, A., Schramm, A., Welsch, H., Hansen, W., Nemcsics, A., and Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest. Mon . "Faceting during GaAs quantum dot self-assembly by droplet epitaxy". United States. doi:10.1063/1.2737123.
@article{osti_20971931,
title = {Faceting during GaAs quantum dot self-assembly by droplet epitaxy},
author = {Heyn, Ch. and Stemmann, A. and Schramm, A. and Welsch, H. and Hansen, W. and Nemcsics, A. and Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest},
abstractNote = {Strain-free GaAs quantum dots (QDs) are grown in a self-assembled fashion by applying Ga droplet epitaxy. The QDs are studied using electron diffraction and atomic force microscopy. Two distinct regimes are observed for the QD shape. QDs whose volume exceeds approximately 3x10{sup 5} Ga atoms are shaped like truncated pyramids with side facets having an angle of about 55 deg. . Smaller QDs are pyramidlike with 25 deg. facets.},
doi = {10.1063/1.2737123},
journal = {Applied Physics Letters},
number = 20,
volume = 90,
place = {United States},
year = {Mon May 14 00:00:00 EDT 2007},
month = {Mon May 14 00:00:00 EDT 2007}
}
  • Two regimes are observed for the density of strain-free GaAs quantum dots (QDs) grown by Ga droplet epitaxy. QDs grown from liquid Ga droplets deposited at temperatures up to 200 deg. C exhibit densities that qualitatively agree with classical nucleation theory and are quantitatively reproduced by a rate equations based growth model under consideration of dimer break off. In contrast, at higher growth temperatures, the onset of coarsening by Ostwald ripening [Z. Phys. Chem., Stoechiom. Verwandtschaftsl. 34, 495 (1900)] causes drastically reduced QD densities. Extension of the growth models and consideration of Ostwald ripening allow the quantitative prediction of QDmore » densities in this regime, as well.« less
  • Laterally aligned, unstrained GaAs/AlGaAs quantum dot molecules (QDMs) are created by droplet epitaxy, utilizing the anisotropic surface potentials of the GaAs (100) surface for the migration of Ga adatoms. Single QDM photoluminescence spectra show a doublet structure, for which effective mass approximation calculations (including the size of the QDM) suggest it originates from molecular orbital energy levels in the QDM.
  • GaAs quantum dot (QD) was grown by droplet epitaxy (DE) method and the excitation power dependence of photoluminescence (PL) were carried out. To investigate the effect of annealing temperature on QDs optical properties, the two step RTA process was carried out in a various temperature range from 800 to 1000 deg. C. As the thermal annealing temperature increases, the PL peak position is blue-shifted due to the change of the composition and size distribution of QDs, and the highest PL intensity is observed at the sample annealed at 900 deg. C. The integrated PL intensity (I{sub PL}) is plotted againstmore » the excitation density in a log-log scale and the slope was calculated.« less
  • We report the self-assembly of triangular GaAs quantum dots (QDs) on (111)A substrates using droplet epitaxy. Shape transition from hexagonal to triangular QDs is observed with increasing crystallizing temperature. The mechanism of the morphological change is discussed in terms of different growth rates of step edges on a (111)A substrate.
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