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Title: Morphological Instability in InAs/GaSb Superlattices due to Interfacial Bonds

Abstract

Synchrotron x-ray diffraction is used to compare the misfit strain and composition in a self-organized nanowire array in an InAs/GaSb superlattice with InSb interfacial bonds to a planar InAs/GaSb superlattice with GaAs interfacial bonds. It is found that the morphological instability that occurs in the nanowire array results from the large misfit strain that the InSb interfacial bonds have in the nanowire array. Based on this result, we propose that tailoring the type of interfacial bonds during the epitaxial growth of III-V semiconductor films provides a novel approach for producing the technologically important morphological instability in anomalously thin layers.

Authors:
;  [1];  [2]; ; ;  [1];  [1];  [2];  [2];  [3]
  1. Department of Physics, University of Houston, Houston, Texas 77204-5005 (United States)
  2. (United States)
  3. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
Publication Date:
OSTI Identifier:
20699377
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 95; Journal Issue: 9; Other Information: DOI: 10.1103/PhysRevLett.95.096104; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; EPITAXY; FILMS; GALLIUM ANTIMONIDES; GALLIUM ARSENIDES; INDIUM ANTIMONIDES; INDIUM ARSENIDES; LAYERS; NANOSTRUCTURES; SEMICONDUCTOR MATERIALS; STRAINS; STRESSES; SUPERLATTICES; SYNCHROTRON RADIATION; X-RAY DIFFRACTION

Citation Formats

Li, J.H., Moss, S.C., Texas Center for Superconductivity and Advanced Materials, University of Houston, Houston, Texas 77204-5002, Stokes, D.W., Caha, O., Bassler, K.E., Ammu, S.L., Texas Center for Superconductivity and Advanced Materials, University of Houston, Houston, Texas 77204-5002, Department of Electrical and Computer Engineering, University of Houston, Houston, Texas 77204-4007, and Bai, J. Morphological Instability in InAs/GaSb Superlattices due to Interfacial Bonds. United States: N. p., 2005. Web. doi:10.1103/PhysRevLett.95.096104.
Li, J.H., Moss, S.C., Texas Center for Superconductivity and Advanced Materials, University of Houston, Houston, Texas 77204-5002, Stokes, D.W., Caha, O., Bassler, K.E., Ammu, S.L., Texas Center for Superconductivity and Advanced Materials, University of Houston, Houston, Texas 77204-5002, Department of Electrical and Computer Engineering, University of Houston, Houston, Texas 77204-4007, & Bai, J. Morphological Instability in InAs/GaSb Superlattices due to Interfacial Bonds. United States. doi:10.1103/PhysRevLett.95.096104.
Li, J.H., Moss, S.C., Texas Center for Superconductivity and Advanced Materials, University of Houston, Houston, Texas 77204-5002, Stokes, D.W., Caha, O., Bassler, K.E., Ammu, S.L., Texas Center for Superconductivity and Advanced Materials, University of Houston, Houston, Texas 77204-5002, Department of Electrical and Computer Engineering, University of Houston, Houston, Texas 77204-4007, and Bai, J. 2005. "Morphological Instability in InAs/GaSb Superlattices due to Interfacial Bonds". United States. doi:10.1103/PhysRevLett.95.096104.
@article{osti_20699377,
title = {Morphological Instability in InAs/GaSb Superlattices due to Interfacial Bonds},
author = {Li, J.H. and Moss, S.C. and Texas Center for Superconductivity and Advanced Materials, University of Houston, Houston, Texas 77204-5002 and Stokes, D.W. and Caha, O. and Bassler, K.E. and Ammu, S.L. and Texas Center for Superconductivity and Advanced Materials, University of Houston, Houston, Texas 77204-5002 and Department of Electrical and Computer Engineering, University of Houston, Houston, Texas 77204-4007 and Bai, J.},
abstractNote = {Synchrotron x-ray diffraction is used to compare the misfit strain and composition in a self-organized nanowire array in an InAs/GaSb superlattice with InSb interfacial bonds to a planar InAs/GaSb superlattice with GaAs interfacial bonds. It is found that the morphological instability that occurs in the nanowire array results from the large misfit strain that the InSb interfacial bonds have in the nanowire array. Based on this result, we propose that tailoring the type of interfacial bonds during the epitaxial growth of III-V semiconductor films provides a novel approach for producing the technologically important morphological instability in anomalously thin layers.},
doi = {10.1103/PhysRevLett.95.096104},
journal = {Physical Review Letters},
number = 9,
volume = 95,
place = {United States},
year = 2005,
month = 8
}
  • The band edges and band gaps of (InAs){sub n}/(GaSb){sub m} (n,m=1,20) superlattices have been theoretically studied through the plane-wave empirical pseudopotential method for different situations: (i) different substrates, GaSb and InAs; (ii) different point group symmetries, C{sub 2v} and D{sub 2d}; and (iii) different growth directions, (001) and (110). We find that (a) the band gaps for the (001) C{sub 2v} superlattices on a GaSb substrate exhibit a nonmonotonic behavior as a function of the GaSb barrier thickness when the number of (InAs){sub n} layers exceed n=5; (b) substrate effects: compared with the GaSb substrate, the different strain field generatedmore » by the InAs substrate leads to a larger variation of the band gaps for the (001) C{sub 2v} superlattices as a function of the InAs well thickness; (c) effect of the type of interfacial bonds: the In-Sb bonds at the interfaces of the (001) D{sub 2d} superlattices partially pin the band edge states, reducing the influence of the confinement effects on electrons and holes, and lowering the band gaps as compared to the (001) C{sub 2v} case. The valence band maximum of the (001) D{sub 2d} superlattices with Ga-As bonds at the interfaces are shifted down, increasing the band gaps as compared to the (001) C{sub 2v} case; (d) effect of layer orientation: the presence of In-Sb bonds at both interfaces of the (110) superlattices pin the band edge states and reduces the band gaps, as compared to the (001) C{sub 2v} case. An anticrossing between the electron and hole levels in the (110) superlattices, for thin GaSb and thick InAs layers, leads to an increase of the band gaps, as a function of the InAs thickness; (e) superlattices vs random alloys: the comparison between the band edges and band gaps of the superlattices on a GaSb substrate and those for random alloys, lattice matched to a GaSb substrate, as a function of the In composition, shows that the random alloys present almost always higher band gaps and give a clear indication of the effect of superlattice's ordering and period on the behavior of the band gaps and band edges. Inclusion of interfacial interdiffusion, using the approach of Magri and Zunger [Phys. Rev. B 65, 165302 (2002)], is shown to significantly increase the band gaps relative to the predictions for abrupt superlattices, bringing the results closer to experiment. It is noteworthy that k {center_dot} p model fit instead measured gaps corresponding to interdiffused interfaces using a chemically abrupt model.« less
  • We have investigated the effects of interfacial bond configuration on the electronic and structural properties of thin (001)GaSb/InAs superlattices by using state-of-the-art ab initio molecular dynamics techniques to calculate the electronic and structural properties of two twelve-atom model GaSb/InAs superlattices which have been constructed to contain only In-Sb (model 1) or Ga-As (model 2) interface bonds, respectively. We find the strain at the interface to be different in the two cases. In model 1, the In and Sb atoms at the interface move away from each other toward the InAs and GaSb layers, respectively, increasing the interfacial separation (4.3% greatermore » than in bulk InSb) and compressing the back bonds to the atoms in the layer below the interface. In model 2 the Ga and As atoms move toward each other, decreasing the interplanar separation at the interface (3.2% smaller than in bulk GaAs) and stretching the back bonds to the neighboring Sb and In atoms, respectively. We calculate the valence band offset for the Ga-As bonded structure to be 0.15 eV smaller than that for the model containing only In-Sb bonds. This smaller band offset leads to more mixing of As p character into the highest lying valence band of the superlattice and results in a 0.015 eV smaller spin-orbit splitting at the valence band edge of the Ga-As bonded structure. This result is consistent with the 0.05 eV larger band gap observed for Ga-As bonded structures in recent photoconductivity measurements made on both Ga-As and In-Sb bonded samples grown by molecular-beam epitaxy. 16 refs., 1 fig.« less
  • The unique properties of the noncommon-atom InAs/GaSb short-period-superlattices (SPSL) strongly depend on the interface structure. These interfaces are characterized using transmission electron microscopy (TEM). The compositional sharpness is obtained from the comparison of the experimental contrast in g{sub 002} two-beam dark-field TEM images with simulated intensity profiles, which are calculated assuming that the element distribution profiles are described by sigmoidal functions. The interfacial intermixing, defined by the chemical width, is obtained for SPSL with different periods and layer thicknesses, even in the extreme case of nominally less than 3 ML thick InAs layers. Nominal 1 ML InSb layers intentionally insertedmore » are also identified.« less
  • We combine quantitative analyses of Z-contrast images with composition analyses employing atom probe tomography (APT) correlatively to provide a quantitative measurement of atomic scale interfacial intermixing in an InAs/GaSb superlattice (SL). Contributions from GaSb and InAs in the Z-contrast images are separated using an improved image processing technique. Correlation with high resolution APT composition analyses permits an examination of interfacial segregation of both cations and anions and their incorporation in the short period InAs/GaSb SL. Results revealed short, intermediate, and long-range intermixing of In, Ga, and Sb during molecular beam epitaxial growth and their distribution in the SL.