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Title: Self-assembled InAs quantum dots and wires grown on a cleaved-edge GaAs(110) surface

Abstract

We studied the conditions for the Stranski-Krastanov mode of molecular beam epitaxial growth of InAs on a cleaved GaAs(110) surface. Temperature distributions on a subholder with cleaved facets were revealed using thermophotography. Combining these data with a theoretical model enabled a determination of the real temperature on the cleaved-edge surfaces (110), which differed markedly from the temperature on a planar wafer (100). Based on these results, we proposed an approach that combines different growth conditions in one technological process. As a result, appropriate growth conditions were established for InAs quantum dots grown on the cleaved GaAs(110) surface. Control over the dot nucleation process was shown to permit growth of both linear arrays of quantum dots and planar quantum wires on these (110) surfaces.

Authors:
; ; ; ;  [1]
  1. Centre for Advanced Nanotechnology, University of Toronto, 170 College Street, Toronto M53 3E4 (Canada)
Publication Date:
OSTI Identifier:
20795799
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 99; Journal Issue: 9; Other Information: DOI: 10.1063/1.2197027; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CRYSTAL GROWTH; GALLIUM ARSENIDES; INDIUM ARSENIDES; MOLECULAR BEAM EPITAXY; NUCLEATION; QUANTUM DOTS; QUANTUM WIRES; SEMICONDUCTOR MATERIALS; SURFACES; TEMPERATURE DISTRIBUTION

Citation Formats

Blumin, M., Ruda, H.E., Savelyev, I. G., Shik, A., and Wang, H. Self-assembled InAs quantum dots and wires grown on a cleaved-edge GaAs(110) surface. United States: N. p., 2006. Web. doi:10.1063/1.2197027.
Blumin, M., Ruda, H.E., Savelyev, I. G., Shik, A., & Wang, H. Self-assembled InAs quantum dots and wires grown on a cleaved-edge GaAs(110) surface. United States. doi:10.1063/1.2197027.
Blumin, M., Ruda, H.E., Savelyev, I. G., Shik, A., and Wang, H. Mon . "Self-assembled InAs quantum dots and wires grown on a cleaved-edge GaAs(110) surface". United States. doi:10.1063/1.2197027.
@article{osti_20795799,
title = {Self-assembled InAs quantum dots and wires grown on a cleaved-edge GaAs(110) surface},
author = {Blumin, M. and Ruda, H.E. and Savelyev, I. G. and Shik, A. and Wang, H.},
abstractNote = {We studied the conditions for the Stranski-Krastanov mode of molecular beam epitaxial growth of InAs on a cleaved GaAs(110) surface. Temperature distributions on a subholder with cleaved facets were revealed using thermophotography. Combining these data with a theoretical model enabled a determination of the real temperature on the cleaved-edge surfaces (110), which differed markedly from the temperature on a planar wafer (100). Based on these results, we proposed an approach that combines different growth conditions in one technological process. As a result, appropriate growth conditions were established for InAs quantum dots grown on the cleaved GaAs(110) surface. Control over the dot nucleation process was shown to permit growth of both linear arrays of quantum dots and planar quantum wires on these (110) surfaces.},
doi = {10.1063/1.2197027},
journal = {Journal of Applied Physics},
number = 9,
volume = 99,
place = {United States},
year = {Mon May 01 00:00:00 EDT 2006},
month = {Mon May 01 00:00:00 EDT 2006}
}
  • We report on a promising approach for positioning of self-assembled InAs quantum dots on (110) GaAs with nanometer precision. By combining self-assembly of quantum dots with molecular beam epitaxy on previously grown and in situ cleaved substrates (cleaved-edge overgrowth), arrays of long-range ordered InAs quantum dots have been fabricated. Both atomic force microscopy and micro-photoluminescence measurements demonstrate the ability to control size, position, and ordering of the quantum dots. Furthermore, single dot photoluminescence investigations confirm the high optical quality of the quantum dots fabricated.
  • Photoluminescence (PL) at wavelengths over 1.55 μm from self-assembled InAs quantum dots (QDs) grown on GaAs(001) is observed at room temperature (RT) and 4 K using a bilayer structure with thin cap. The PL peak has been known to redshift with decreasing cap layer thickness, although accompanying intensity decrease and peak broadening. With our strain-controlled bilayer structure, the PL intensity can be comparable to the ordinary QDs while realizing peak emission wavelength of 1.61 μm at 4 K and 1.73 μm at RT. The key issue lies in the control of strain not only in the QDs but also in the cap layer. By combiningmore » with underlying seed QD layer, we realize strain-driven bandgap engineering through control of strain in the QD and cap layers.« less
  • We calculate the electronic structures of pyramidal quantum dots with supercells containing 250000 atoms, using spin-orbit-coupled, nonlocal, empirical pseudopotentials. We compare the results with previous theoretical calculations. Our calculation circumvents the approximations underlying the conventional effective-mass approach: we describe the potential, the strain and the wave functions using atomistic rather than continuum models. The potential is given by a superposition of screened atomic pseudopotentials, the strain is obtained from minimizing the atomistic strain energy, and the wave function is expanded using a plane-wave basis set. We find the following. (1) The conduction bands are formed essentially from single envelope functions,more » so they can be classified according to the nodal structure as s, p, and {ital d}. However, due to strong multiband coupling, most notably light hole with heavy hole, the valence states cannot be classified in the language of single-band envelope functions. In fact, the hole states have no nodal planes. (2) There is a strong anisotropy in the polarization of the lowest valence state to conduction state optical transition. This is in contrast to the eight band {bold k}{center_dot}{bold p} model, which finds essentially zero anisotropy. (3) There are at least four bound electron states for a 113-{Angstrom}-based quantum dot. This number of bound states is larger than that found in eight band {bold k}{center_dot}{bold p} calculations. (4) Since our atomistic description retains the correct C{sub 2v} symmetry of a square-based pyramid made of zinc-blende solids, we find that the otherwise degenerate {ital p} states are split by about 25 meV. This splitting is underestimated in the eight-band {bold k}{center_dot}{bold p} calculation. {copyright} {ital 1999} {ital The American Physical Society}« less
  • The structure-performance properties of single-layered and multi-layered InAs/GaAs{sub 1−x}Sb{sub x} quantum dot (QD) system, grown by molecular beam epitaxy on GaAs (001) substrates, have been investigated as a function of Sb concentration. Electron microscopy observations showed no significant crystalline defects for the single-layered InAs QDs (Sb 20%). X-ray diffraction analysis revealed that the increase of Sb concentration from 7.3% to 10.2% for the multi-layered QDs increased the strain relaxation from 0% to ∼23% and the dislocation density of GaAsSb layers went up to 3.6 × 10{sup 9 }cm{sup −2}. The peak energy of QD luminescence was red-shifted with increasing Sb concentration due tomore » reduced strain inside QDs. Moreover, the carrier lifetime of the QDs was highly improved from 1.7 to 36.7 ns due to weak hole confinement as the Sb concentration was increased from 7.3% to 10.2%. These structures should be highly promising as the basis for photovoltaic solar-cell applications. Finally, the increased Sb concentration increased the thermal activation energy of electrons confined in the QDs from 163.7 to 206.8 meV, which was indicative of the improved thermal stability with Sb concentration.« less
  • A two-stage 'nucleation-augmented' growth method for producing InAs self-assembled quantum dots (QDs) using molecular-beam epitaxy on GaAs (100) substrates has been investigated in detail. Photoluminescence (PL) measurements show that a 1.8-monolayer-(MLs) InAs QD 'nucleation' layer grown at a fast rate, followed by a 2.6-MLs-InAs 'augmented' layer grown under pulsed conditions at a slow rate, dramatically increases the dot density and improves the PL intensity for the InAs QDs. It was found that, when the effective growth rate of the InAs augmented layer was reduced, the PL peak emission shifts to a longer wavelength and the PL intensity is enhanced. Thesemore » changes in characteristics were attributed to improved optical quality and greater dot density.« less