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(322) Production(s) de GIL B.
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Quantitative interpretation of the excitonic splitting in aluminum nitride
Auteur(s): Gil B., Guizal B., Felbacq D., Bouchitté Guy
(Article) Publié:
The European Physical Journal Applied Physics, vol. 53 p.3 (2011)
Texte intégral en Openaccess :
Ref HAL: hal-00633617_v1
DOI: 10.1051/epjap/2010100448
WoS: 000288591700003
Exporter : BibTex | endNote
10 Citations
Résumé: We address the interpretation of the splitting between the ground state excitonic transition which indicates the energy of the lowest direct band gap in AlN bulk films and epilayers, and a 36-38 meV higher energy companion. We demonstrate that this splitting is consistent with the initial interpretation in terms of 1s - 2s excitonic splitting by using a calculation of the exciton binding energy which includes mass anisotropy and anisotropy of the dielectric constant. Analytical expressions are proposed to compute the evolution of 1s and 2s excitonic energies using an anisotropy parameter . We show that the values of the dielectric constant that are required to fit the data are 8.7 and 10, values different from the couple of values 7.33 and 8.45 erroneously obtained after a fitting procedure using a spherical description of the long range Coulomb interaction and the classical textbook n-2 spectrum of the excitonic eigenstates. Starting from now, our values are the recommended ones.
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Internal structure of acceptor-bound excitons in wide-band-gap wurtzite semiconductors
Auteur(s): Gil B., Bigenwald Pierre, Paskov Plamen P., Monemar Bo
(Article) Publié:
Physical Review B, vol. 81 p.085211 (2010)
Texte intégral en Openaccess :
Ref HAL: hal-00546329_v1
DOI: 10.1103/PhysRevB.81.085211
WoS: 000275053300064
Exporter : BibTex | endNote
9 Citations
Résumé: We describe the internal structure of acceptor-bound excitons in wurtzite semiconductors. Our approach consists in first constructing, in the context of angular momentum algebra, the wave functions of the two-hole system that fulfill Pauli's exclusion's principle. Second, we construct the acceptor-bound exciton states by adding the electron states in a similar manner that two-hole states are constructed. We discuss the optical selection rules for the acceptor-bound exciton recombination. Finally, we compare our theory with experimental data for CdS and GaN. In the specific case of CdS for which much experimental information is available, we demonstrate that, compared with cubic semiconductors, the sign of the short-range hole-exchange interaction is reversed and more than one order of magnitude larger. The whole set of data is interpreted in the context of a large value of the short-range hole-exchange interaction Xi(0)=3.4 +/- 0.2 meV. This value dictates the splitting between the ground-state line I-1 and the other transitions. The values we find for the electron-hole spin-exchange interaction and of the crystal-field splitting of the two-hole state are, respectively, -0.4 +/- 0.1 and 0.2 +/- 0.1 meV. In the case of GaN, the experimental data for the acceptor-bound excitons in the case of Mg and Zn acceptors, show more than one bound-exciton line. We discuss a possible assignment of these states.
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Hydrostatic deformation potentials and the question of exciton binding energies and splittings in aluminium nitride
Auteur(s): Gil B.
(Article) Publié:
Physical Review B, vol. 81 p.205201 (2010)
Ref HAL: hal-00546326_v1
DOI: 10.1103/PhysRevB.81.205201
WoS: 000278144500039
Exporter : BibTex | endNote
16 Citations
Résumé: By comparing a series of optical experiments performed on bulk aluminum nitride crystals and heteroepitaxial films, we determine the hydrostatic excitonic deformation potentials of AlN. The agreement between the whole available experimental data and our analysis consolidates this determination. Using the previously determined values of the valence-band deformation potentials which account for the strain-induced variation in the crystal-field splitting: d(3)=-8.19 eV and d(4)=4.10 eV we obtain values of -6.04 and 2.15 eV for the hydrostatic excitonic deformation potentials a(1) and a(2) in the context of the quasicubic approximation. This constitutes the first series of values coherent with the whole set of experimental data. The experimental value of 1s-2s splitting disagrees with the theory of excitons in anisotropic semiconductors. This disagreement, we attribute it to our poor knowledge of the valence-band dispersion relations of AlN and to the difficulty we face for including in the calculation plausible values for the anisotropic hole effective mass, dielectric constant.
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Determination of piezoelectric and spontaneous polarization fields in CdxZn1-xO/ZnO quantum wells grown along the polar < 0001 > direction
Auteur(s): Benharrats F., Zitouni K., Kadri A., Gil B.
(Article) Publié:
Superlattices And Microstructures, vol. 47 p.592-596 (2010)
Texte intégral en Openaccess :
Ref HAL: hal-00546321_v1
DOI: 10.1016/j.spmi.2010.01.007
WoS: 000278037900004
Exporter : BibTex | endNote
43 Citations
Résumé: By iteratively solving the Schrodinger and Poisson equations, we determine theoretical values of built-in electric field induced by spontaneous and piezoelectric polarizations in wurtzite CdxZn1-xO/ZnO (x <= 0.2) quantum wells (QWs) grown along < 0001 > polar direction. By adjusting recent photoluminescence data, we find that this internal field increases with x with a linear slope A = 17.83 MV/cm. Spontaneous and piezoelectric polarization variations are also determined together with the sheet charge densities at CdxZn1-xO/ZnO heterointerface. Our results indicate similar, but much stronger polarization effects than previously reported for MgxZn1-xO/ZnO QWs. They constitute record polarization effects ever reported for wide bandgap heterostructures, including group III-nitrides. (C) 2010 Elsevier Ltd. All rights reserved.
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Plasmon-induced Purcell effect in InN/In metal-semiconductor nanocomposites
Auteur(s): Shubina T. V., Toropov A. A., Jmerik V. N., Kuritsyn D. I., Gavrilenko L. V., Krasil'Nik Z. F., Araki T., Nanishi Y., Gil B., Govorov A. O., Ivanov S. V.
(Article) Publié:
Physical Review B, vol. 82 p.073304 (2010)
Ref HAL: hal-00546318_v1
DOI: 10.1103/PhysRevB.82.073304
WoS: 000280849600001
Exporter : BibTex | endNote
23 Citations
Résumé: The Purcell effect, acceleration of a spontaneous emission recombination rate, has been observed in InN/In nanocomposites with buried nanoparticles of metallic In. This effect, associated with localized plasmons, is characterized by the averaged Purcell factor as high as 30-40 in the structures with large enough particles. This high value is indicative of a noticeable contribution from the emitting dipoles polarized normally to the nanoparticle surface in this system. The experimental observation of shortening of the emission lifetimes with increasing the amount of In is supported by calculations performed in a semiclassical approximation.
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Strong exciton-photon coupling in ZnO microcavities : Promoting polariton physics up to 300K
Auteur(s): Guillet T., Faure Stéphane, Brimont C., Bretagnon T., Gil B., Zúñiga-Pérez Jesús, Frayssinet Eric, Semond Fabrice, Leroux Mathieu, Bouchoule Sophie
Conference: 9th Japan-France Workshop on Nanomaterials (Toulouse, FR, 2010-11-24)
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MOVPE growth and characterization of indium nitride on C-, A-, M-, and R-plane sapphire
Auteur(s): Moret M., Ruffenach S., Briot O., Gil B.
Conference: Symposium on Group III Nitride Semiconductors held at the 2009 EMRS Spring Meeting (Strasbourg (FRANCE), FR, 2009-06-08)
Actes de conférence: PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, vol. 207 p.24-28 (2010)
Ref HAL: hal-00540220_v1
Exporter : BibTex | endNote
Résumé: We have investigated the heteroepitaxial growth of indium nitride on sapphire substrates having different orientations. Growths were performed on C-, A-, M-, and R-plane-oriented sapphire in order to analyze the substrate orientation effect on the structural, optical, and electronic properties of InN. The orientation relationship between InN and sapphire was deduced by theta/2 theta High-resolution X-ray diffraction (HRXRD) measurements. These experiments show the ability to grow InN along nonpolar (11 (2) under bar0) orientation and the semipolar (11 (2) under bar2) orientation, depending of the orientations of the sapphire substrate. The crystalline quality was assessed by XRD symmetric and asymmetric rocking curve. measurements. We observed no drastic disparity between our samples, all exhibiting a reasonable crystalline quality. Atomic force microscopy imaging on these, layers, revealed different surface morphologies with a roughness varying between 30 and 60 nm. Electrical properties of the InN samples were investigated by room temperature Hall effbt.Cmeasourements and a line shape fitting of the photoluminescence was performed in order to get optically the values of the residual carrier density in the nitride layers. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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