skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Effect of interwire separation on growth kinetics and properties of site-selective GaAs nanowires

Abstract

We report tuning of the growth kinetics, geometry, and properties of autocatalytic GaAs nanowires (NW) by precisely controlling their density on SiO{sub 2}-mask patterned Si (111) substrates using selective area molecular beam epitaxy. Using patterned substrates with different mask opening size (40–120 nm) and pitch (0.25–3 μm), we find that the NW geometry (length, diameter) is independent of the opening size, in contrast to non-catalytic GaAs NWs, whereas the NW geometry strongly depends on pitch, i.e., interwire separation and NW density. In particular, two distinct growth regimes are identified: a diffusion-limited regime for large pitches (low NW density) and a competitive growth regime for smaller pitches (high NW density), where axial and radial NW growth rates are reduced. The transition between these two regimes is significantly influenced by the growth conditions and shifts to smaller pitches with increasing As/Ga flux ratio. Ultimately, the pitch-dependent changes in growth kinetics lead to distinctly different photoluminescence properties, highlighting that mask template design is a very critical parameter for tuning intrinsic NW properties.

Authors:
; ; ; ; ; ; ; ;  [1];  [1];  [2]
  1. Walter Schottky Institut and Physik Department, Technische Universität München, Garching 85748 (Germany)
  2. (Germany)
Publication Date:
OSTI Identifier:
22311158
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 3; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; CRYSTAL GROWTH; DIFFUSION; GALLIUM ARSENIDES; MOLECULAR BEAM EPITAXY; NANOWIRES; PHOTOLUMINESCENCE; QUANTUM WIRES; SILICA; SILICON OXIDES; SUBSTRATES

Citation Formats

Rudolph, D., Schweickert, L., Morkötter, S., Loitsch, B., Hertenberger, S., Becker, J., Bichler, M., Finley, J. J., Koblmüller, G., E-mail: Gregor.Koblmueller@wsi.tum.de, Abstreiter, G., and Institute for Advanced Study, Technische Universität München, Garching 85748. Effect of interwire separation on growth kinetics and properties of site-selective GaAs nanowires. United States: N. p., 2014. Web. doi:10.1063/1.4891427.
Rudolph, D., Schweickert, L., Morkötter, S., Loitsch, B., Hertenberger, S., Becker, J., Bichler, M., Finley, J. J., Koblmüller, G., E-mail: Gregor.Koblmueller@wsi.tum.de, Abstreiter, G., & Institute for Advanced Study, Technische Universität München, Garching 85748. Effect of interwire separation on growth kinetics and properties of site-selective GaAs nanowires. United States. doi:10.1063/1.4891427.
Rudolph, D., Schweickert, L., Morkötter, S., Loitsch, B., Hertenberger, S., Becker, J., Bichler, M., Finley, J. J., Koblmüller, G., E-mail: Gregor.Koblmueller@wsi.tum.de, Abstreiter, G., and Institute for Advanced Study, Technische Universität München, Garching 85748. Mon . "Effect of interwire separation on growth kinetics and properties of site-selective GaAs nanowires". United States. doi:10.1063/1.4891427.
@article{osti_22311158,
title = {Effect of interwire separation on growth kinetics and properties of site-selective GaAs nanowires},
author = {Rudolph, D. and Schweickert, L. and Morkötter, S. and Loitsch, B. and Hertenberger, S. and Becker, J. and Bichler, M. and Finley, J. J. and Koblmüller, G., E-mail: Gregor.Koblmueller@wsi.tum.de and Abstreiter, G. and Institute for Advanced Study, Technische Universität München, Garching 85748},
abstractNote = {We report tuning of the growth kinetics, geometry, and properties of autocatalytic GaAs nanowires (NW) by precisely controlling their density on SiO{sub 2}-mask patterned Si (111) substrates using selective area molecular beam epitaxy. Using patterned substrates with different mask opening size (40–120 nm) and pitch (0.25–3 μm), we find that the NW geometry (length, diameter) is independent of the opening size, in contrast to non-catalytic GaAs NWs, whereas the NW geometry strongly depends on pitch, i.e., interwire separation and NW density. In particular, two distinct growth regimes are identified: a diffusion-limited regime for large pitches (low NW density) and a competitive growth regime for smaller pitches (high NW density), where axial and radial NW growth rates are reduced. The transition between these two regimes is significantly influenced by the growth conditions and shifts to smaller pitches with increasing As/Ga flux ratio. Ultimately, the pitch-dependent changes in growth kinetics lead to distinctly different photoluminescence properties, highlighting that mask template design is a very critical parameter for tuning intrinsic NW properties.},
doi = {10.1063/1.4891427},
journal = {Applied Physics Letters},
number = 3,
volume = 105,
place = {United States},
year = {Mon Jul 21 00:00:00 EDT 2014},
month = {Mon Jul 21 00:00:00 EDT 2014}
}
  • Anisotropic selective epitaxy in nanoscale-patterned growth (NPG) by molecular-beam epitaxy is investigated on a 355 nm period two-dimensional array of circular holes fabricated in a 30-nm-thick SiO{sub 2} film on a GaAs(001) substrate. The hole diameter ranged from 70 to 150 nm. The small hole diameter and the very thin masking layer stimulated lateral growth over the SiO{sub 2} surface at an early stage of selective epitaxy on this patterned substrate. Lateral overgrowth associated with selective epitaxy, however, did not proceed isotropically along the circular boundary between the open substrate surface and the SiO{sub 2} mask. There was preferential growthmore » direction parallel to <111>B. This anisotropy in the selective epitaxy resulted in the formation of a nanoscale, nontapered, straight-wire-type epitaxial layer (GaAs nanowires), which had a length of up to 1.8 {mu}m for a nominal 200 nm deposition. Every GaAs nanowire had a hexagonal prismatic shape directed along <111>B and was surrounded by six (110) sidewalls. The anisotropy of selective epitaxy and faceting in NPG were affected by the profile of the SiO{sub 2} mask and are interpreted using a minimization of the total surface energy for equilibrium crystal shape.« less
  • We prepared InAs nanowires (NWs) by lateral growth on GaAs (110) masked substrates in molecular beam epitaxy. We measured magneto-transport properties of the InAs NWs. In spite of parallel-NW multi-channels, we observed fluctuating magneto-conductance. From the fluctuation, we evaluated phase coherence length as a function of measurement temperature, and found decrease in the length with increase in the temperature. We also evaluate phase coherence length as a function of gate voltage.
  • The growth and optical properties of InP and InP/InAs nanostructures on GaAs nanowires are investigated. InP quantum well and quantum dots (QDs) are formed on the sidewalls of GaAs nanowires successively with increasing the deposition time of InP. The GaAs/InP nanowire heterostructure exhibits a type-II band alignment. The wavelength of the InP quantum well is in the range of 857–892 nm at 77 K, which means that the quantum well is nearly fully strained. The InP quantum dot, which has a bow-shaped cross section, exhibits dislocation-free pure zinc blende structure. Stranski-Krastanow InAs quantum dots are subsequently formed on the GaAs/InP nanowire core-shellmore » structure. The InAs quantum dots are distributed over the middle part of the nanowire, indicating that the In atoms contributing to the quantum dots mainly come from the vapor rather than the substrate. The longest emission wavelength obtained from the InAs QDs is 1039 nm at 77 K. The linewidth is as narrow as 46.3 meV, which is much narrower than those on planar InP substrates and wurtzite InP nanowires, suggesting high-crystal-quality, phase-purity, and size-uniformity of quantum dots.« less
  • GaAs nanowires were grown on (111)B GaAs substrates using the vapour-liquid-solid mechanism. The Au/Pt nanodots used to catalyse wire growth were defined lithographically and had varying diameter and separation. An in-depth statistical analysis of the resulting nanowires, which had a cone-like shape, was carried out. This revealed that there were two categories of nanowire present, with differing height and tapering angle. The bimodal nature of wire shape was found to depend critically on the diameter of the Au-Ga droplet atop the nanowire. Transmission electron microscopy analysis also revealed that the density of stacking faults in the wires varied considerably betweenmore » the two categories of wire. It is believed that the cause of the distinction in terms of shape and crystal structure is related to the contact angle between the droplet and the solid-liquid interface. The dependency of droplet diameter on contact angle is likely related to line-tension, which is a correction to Young's equation for the contact angle of a droplet upon a surface. The fact that contact angle may influence resulting wire structure and shape has important implications for the planning of growth conditions and the preparation of wires for use in proposed devices.« less
  • We report the effects of variations in As{sub 4} growth flux on the evolution of molecular beam epitaxy grown InAs quantum dots (QDs) and their structures and optical properties. For InAs QDs grown under As-stable conditions, evaluated through photoluminescence and atomic force microscopy (AFM) measurements, it is evident that QD size increases with As{sub 4} pressure along with improvement in size uniformity. Furthermore, transmission electron microscopy measurements for InAs layers of critical thicknesses ({approx}1.7 ML) showed decreasing QD density with increasing As{sub 4} pressure accompanied by a strong reduction in photoluminescence (PL) integral intensity. These show that high As{sub 4}more » fluxes suppress InAs QD formation while the decreasing PL intensity seems to indicate cluster formation that features nonradiative recombination. AFM measurements show larger and denser QDs for samples grown at higher As{sub 4} pressures. These are explained on the basis of adatom condensation during surface cooling and the influence of As{sub 4} pressure on indium incorporation.« less