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Title: Formation of InAs/GaAs quantum dots from a subcritical InAs wetting layer: A reflection high-energy electron diffraction and theoretical study

Abstract

InAs/GaAs quantum dots (QD's) are formed by postgrowth annealing of an InAs wetting layer thinner than the critical thickness for the transition from two- (2D) to three-dimensional (3D) growth mode. Reflection high energy electron diffraction is used to monitor the QD formation. Based on a mean-field theory [Phys. Rev. Lett. 79, 897 (1997)], the time evolution of total QD's volume, first increasing and finally saturating, is well explained by precursors forming during wetting layer growth and converting into nucleated QD's after growth stop. Both the saturation QD's volume and the QD nucleation rate depend exponentially on the InAs coverage. These behaviors and their temperature and InAs growth rate dependences are essentially understandable in the frame of the mean-field theory. Similar analysis to conventional QD growth suggests that the often observed significant mass transport from wetting layer to QD's can be ascribed to the precursors existing before 2D-3D growth mode transition.

Authors:
; ; ; ; ;  [1];  [2];  [2];  [2]
  1. Nanotechnology Research Center, Fujitsu Lab. Ltd., Morinosato-Wakamiya 10-1, Atsugi, Kanagawa 243-0197 (Japan)
  2. (Japan)
Publication Date:
OSTI Identifier:
20788008
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 73; Journal Issue: 11; Other Information: DOI: 10.1103/PhysRevB.73.115327; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; CRYSTAL GROWTH; ELECTRON DIFFRACTION; GALLIUM ARSENIDES; INDIUM ARSENIDES; LAYERS; MEAN-FIELD THEORY; NUCLEATION; QUANTUM DOTS; REFLECTION; SEMICONDUCTOR MATERIALS

Citation Formats

Song, H. Z., Usuki, T., Nakata, Y., Yokoyama, N., Sasakura, H., Muto, S., and CREST, Japan Science and Technology Agency, Kawaguchi 332-0012, Nanotechnology Research Center, Fujitsu Lab. Ltd., Morinosato-Wakamiya 10-1, Atsugi, Kanagawa 243-0197, and Department of Applied Physics, Hokkaido University, Sapporo 060-8628, Japan, and CREST, Japan Science and Technology Agency, Kawaguchi 332-0012. Formation of InAs/GaAs quantum dots from a subcritical InAs wetting layer: A reflection high-energy electron diffraction and theoretical study. United States: N. p., 2006. Web. doi:10.1103/PHYSREVB.73.1.
Song, H. Z., Usuki, T., Nakata, Y., Yokoyama, N., Sasakura, H., Muto, S., and CREST, Japan Science and Technology Agency, Kawaguchi 332-0012, Nanotechnology Research Center, Fujitsu Lab. Ltd., Morinosato-Wakamiya 10-1, Atsugi, Kanagawa 243-0197, & Department of Applied Physics, Hokkaido University, Sapporo 060-8628, Japan, and CREST, Japan Science and Technology Agency, Kawaguchi 332-0012. Formation of InAs/GaAs quantum dots from a subcritical InAs wetting layer: A reflection high-energy electron diffraction and theoretical study. United States. doi:10.1103/PHYSREVB.73.1.
Song, H. Z., Usuki, T., Nakata, Y., Yokoyama, N., Sasakura, H., Muto, S., and CREST, Japan Science and Technology Agency, Kawaguchi 332-0012, Nanotechnology Research Center, Fujitsu Lab. Ltd., Morinosato-Wakamiya 10-1, Atsugi, Kanagawa 243-0197, and Department of Applied Physics, Hokkaido University, Sapporo 060-8628, Japan, and CREST, Japan Science and Technology Agency, Kawaguchi 332-0012. Wed . "Formation of InAs/GaAs quantum dots from a subcritical InAs wetting layer: A reflection high-energy electron diffraction and theoretical study". United States. doi:10.1103/PHYSREVB.73.1.
@article{osti_20788008,
title = {Formation of InAs/GaAs quantum dots from a subcritical InAs wetting layer: A reflection high-energy electron diffraction and theoretical study},
author = {Song, H. Z. and Usuki, T. and Nakata, Y. and Yokoyama, N. and Sasakura, H. and Muto, S. and and CREST, Japan Science and Technology Agency, Kawaguchi 332-0012 and Nanotechnology Research Center, Fujitsu Lab. Ltd., Morinosato-Wakamiya 10-1, Atsugi, Kanagawa 243-0197 and Department of Applied Physics, Hokkaido University, Sapporo 060-8628, Japan, and CREST, Japan Science and Technology Agency, Kawaguchi 332-0012},
abstractNote = {InAs/GaAs quantum dots (QD's) are formed by postgrowth annealing of an InAs wetting layer thinner than the critical thickness for the transition from two- (2D) to three-dimensional (3D) growth mode. Reflection high energy electron diffraction is used to monitor the QD formation. Based on a mean-field theory [Phys. Rev. Lett. 79, 897 (1997)], the time evolution of total QD's volume, first increasing and finally saturating, is well explained by precursors forming during wetting layer growth and converting into nucleated QD's after growth stop. Both the saturation QD's volume and the QD nucleation rate depend exponentially on the InAs coverage. These behaviors and their temperature and InAs growth rate dependences are essentially understandable in the frame of the mean-field theory. Similar analysis to conventional QD growth suggests that the often observed significant mass transport from wetting layer to QD's can be ascribed to the precursors existing before 2D-3D growth mode transition.},
doi = {10.1103/PHYSREVB.73.1},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 11,
volume = 73,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}
  • Self-assembling process of InAs/GaAs quantum dots has been investigated by analyzing reflection high-energy electron diffraction chevron images reflecting the crystal facet structure surrounding the island. The chevron image shows dramatic changes during the island formation. From the temporal evolution of the chevron tail structure, the self-assembling process has been found to consist of four steps. The initial islands do not show distinct facet structures. Then, the island surface is covered by high-index facets, and this is followed by the formation of stable low-index facets. Finally, the flow of In atoms from the islands occurs, which contributes to flatten the wettingmore » layer. Furthermore, we have investigated the island shape evolution during the GaAs capping layer growth by using the same real-time analysis technique.« less
  • Dynamic images of InAs quantum dots (QDs) formation are obtained using a unique scanning tunneling microscope (STM) placed within the growth chamber. These images are interpreted with the aid of kinetic Monte Carlo (kMC) simulations of the QD nucleation process. Alloy fluctuations in the InGaAs wetting layer prior to QD formation assist in the nucleation of stable InAs islands containing tens of atoms which grow extremely rapidly to form QDs. Furthermore, not all deposited In is initially incorporated into the lattice, providing a large supply of material to rapidly form QDs at the critical thickness.
  • The authors report on the impact of wetting layer thickness and quantum dot size on the electronic and optical properties of dome-shaped InAs/GaAs quantum dots (QDs) with strained potential. Two wetting layer thicknesses of 0.5 and 2.0 nm were compared. A strong size dependence of P-to-S transition energy, transition dipole moment, oscillator strength, and linear and third-order nonlinear susceptibilities were concluded. The P-to-S transition dipole moment was shown to be purely in-plane polarization. The linear and nonlinear absorption and dispersion showed a red shift when the wetting layer thickness was increased. Our results revealed that the nonlinear susceptibility is muchmore » more sensitive to QD size compared to the linear susceptibility. An interpretation of the results was presented based on the probability density of finding the electron inside the dot and wetting layer. The results are in good agreement with previously reported experimental data.« less
  • In this work, the effects of the shape and size on the intersubband electronic and optical properties of three-dimensional self-assembled pyramid-shaped InAs/GaAs quantum dots (QDs) were investigated in detail. More precisely, in-plane- and z-polarized transitions dipole moment (TDM), oscillator strength (OS), and absorption coefficients of P-to-S, WL-to-P, and WL-to-S transitions were studied as a function of the QD height. The P-to-S TDM showed to be strong and purely in-plane-polarized transition dominating two others. However, the TDMs and OSs of WL-to-P and WL-to-S transitions which are in-plane- and z-polarized transitions, respectively, showed a competition behavior for short and tall QDs. Themore » former dominates for short QDs, and the latter for tall QDs. The physical reasons behind these interesting phenomena were also explained using the probability of finding the carriers in the pyramid region attached to the WL. The theoretical results are in good agreement with experimental data reported for short QDs [Appl. Phys. Lett. 82, 630 (2003)].« less
  • A technique of arsenic-induced RHEED intensity oscillations has been used to accurately measure arsenic incorporation rates as a function of substrate temperature during the homoepitaxial growths of both GaAs and InAs by molecular beam epitaxy (MBE). Measurements were made at growth temperatures from 350 to 650 C and at arsenic fluxes of 0.1 to 10.0 monolayer/s. The method measures only the arsenic actually incorporated into the growing film and does not include the arsenic lost in splitting the arsenic tetramers or lost by evaporation from the sample. 9 references.