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10 results on '"V V Chaldyshev"'

1. Long coherent dynamics of localized excitons in (In,Ga)N/GaN quantum wells

Author

Manfred Bayer, Dmitri R. Yakovlev, W. V. Lundin, I. A. Solovev, S. V. Poltavtsev, I. A. Akimov, A. V. Sakharov, A. F. Tsatsul’nikov, and V. V. Chaldyshev

Subjects
Physics, Condensed Matter::Quantum Gases, Coherence time, Photon, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter::Other, Exciton, Resolution (electron density), chemistry.chemical_element, FOS: Physical sciences, 02 engineering and technology, 021001 nanoscience & nanotechnology, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 01 natural sciences, Condensed Matter::Materials Science, chemistry, Homogeneous, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Atomic physics, 010306 general physics, 0210 nano-technology, Quantum well, Indium, Energy (signal processing)
Abstract

We study the coherent dynamics of localized excitons in 100-periods of 2.5 nm thick (In,Ga)N/GaN quantum wells with 7.5% indium concentration, measured with spectroscopic resolution through two-pulse and three-pulse photon echoes at the temperature of 1.5 K. A long-lived coherent exciton dynamics is observed in the (In,Ga)N quantum wells: When the laser photon energy is tuned across the 43 meV-wide inhomogeneously broadened resonance line, the coherence time T2 varies between 45 and 255 ps, increasing with stronger exciton localization. The corresponding narrow homogeneous linewidths ranging from 5.2 to 29 {\mu}eV as well as the relatively weak exciton-phonon interaction (0.8 {\mu}eV/K) confirm a strong, quantum dot-like exciton localization in a static disordered potential inside the (In,Ga)N quantum well layers., Comment: 4 figs

Published
2018

2. Optical spectroscopy of a semi-insulating GaAs/AlGaAs multiple quantum well system near double exciton–polariton and Bragg resonance

Author

V. P. Evtikhiev, V. V. Chaldyshev, A. S. Shkolnik, and Todd Holden

Subjects
Condensed Matter::Quantum Gases, Materials science, Condensed Matter::Other, business.industry, Exciton, Bragg's law, Optical polarization, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Condensed Matter Physics, Polarization (waves), Atomic and Molecular Physics, and Optics, Spectral line, Electronic, Optical and Magnetic Materials, Optics, Polariton, Electrical and Electronic Engineering, Atomic physics, business, Refractive index, Quantum well
Abstract

We studied optical reflection (OR) and contactless electroreflection (CER) from a periodic system of multiple GaAs/AlGaAs quantum wells (QWs). The QW width was 15 or 20 nm and the barriers were 104 nm thick. In this system the electromagnetic resonance of Bragg reflection occurs at the frequency that coincides or is close to the frequency of the exciton–polariton resonance in the wells. The optical measurements were made at various temperatures, angles of the light incidence and polarization. The optical reflection spectra have been found to be a result of the interplay of three different contributions, namely (i) the reflection from the air/semiconductor interface, (ii) the Bragg reflection due to periodic modulation of the background indices of refraction being different for the wells and barriers and (iii) the resonant reflection from the periodic system of exciton–polaritons in quantum wells. The latter contribution was separately studied by CER technique in the spectral range covering ground states of the heavy-hole and light-hole excitons. A quantitative analysis of the experimental CER line shape has been done along with quantum-mechanical calculations, which revealed the characteristic energies and broadening parameters for different exciton–polariton levels. In particular, the systems of four and 32 QWs exhibit spectral features with the characteristic broadening of 1.8 meV and 2.2 meV at 17 K, respectively. By comparison with theoretical calculations we discuss the radiative and non-radiative contributions to the total broadening.

Published
2007

3. Micro-raman investigation of the n-dopant distribution in lateral epitaxial overgrown GaN/sapphire (0001)

Author

Ian T. Ferguson, S. P. Gou, V. V. Chaldyshev, Fred H. Pollak, and Milan Pophristic

Subjects
Materials science, Dopant, business.industry, Doping, Analytical chemistry, Nitride, Condensed Matter Physics, Epitaxy, Electronic, Optical and Magnetic Materials, symbols.namesake, Thermal conductivity, Materials Chemistry, Sapphire, symbols, Optoelectronics, Electrical and Electronic Engineering, Spectroscopy, business, Raman spectroscopy
Abstract

We have investigated the n-dopant distribution in the overgrown and window regions of lateral-epitaxial overgrown GaN/sapphire (0001) using room-temperature micro-Raman spectroscopy in the backscattering configuration. From a fit to the high energy-coupled longitudinal optical (LO) phonon-plasmon mode (LPP+), we have evaluated n ≈ (6.5 ± 0.6) × 1017 cm-3 in the overgrown region; a value considerably higher than that previously reported by Pophristic et al. The spectrum from the window region was harder to interpret because of the considerable overlap of the A1(LO) mode and Eg(750 cm-1) sapphire line with the LPP+ trace. The implications of our findings for the overgrown region on the measured thermal conductivity as well as other parameters will be discussed.

Published
2002

4. Determination of stress, strain, and elemental distribution within In(Ga)As quantum dots embedded in GaAs using advanced transmission electron microscopy

Author

Nikolay Cherkashin, B. R. Semyagin, V. V. Chaldyshev, Martin Hÿtch, V. V. Preobrazhenskii, Alain Claverie, Shay Reboh, Mikhail A. Putyato, Matériaux et dispositifs pour l'Electronique et le Magnétisme (CEMES-MEM), Centre d'élaboration de matériaux et d'études structurales (CEMES), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Interférométrie, In situ et Instrumentation pour la Microscopie Electronique (CEMES-I3EM), A.V. Rzhanov Institute of Semiconductor Physics, A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] (RAS), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), and Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)

Subjects
010302 applied physics, Materials science, Physics and Astronomy (miscellaneous), business.industry, Stress–strain curve, Nanotechnology, 02 engineering and technology, 021001 nanoscience & nanotechnology, Overburden pressure, 01 natural sciences, Gallium arsenide, Core (optical fiber), chemistry.chemical_compound, chemistry, Quantum dot, Transmission electron microscopy, 0103 physical sciences, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Optoelectronics, Wetting, 0210 nano-technology, business, Wetting layer
Abstract

International audience; Non-truncated pyramidal In(Ga)As quantum dots (QDs) embedded in GaAs were obtained by a combination of low temperature/high rate GaAs covering of InAs QDs. We use advanced transmission electron microscopy to study the composition and mechanics of the objects. Results from the core region of a sliced QD, and from an entire object, are consistent and complementary allowing the development of accurate models describing the 3D shape, chemical distribution, elastic strains and stresses in the QD, wetting layer, and matrix. The measured structure develops an extremely compressive apex, reaching a vertical stress of −8 GPa and horizontal stress of −6.2 GPa.

Published
2013

5. Research of resonant light reflection by a periodic system of GaAs/AlGaAs quantum wells

Author

V. V. Chaldyshev, A. A. Kondikov, and P. A. Tonkaev

Subjects
Physics, History, business.industry, Light reflection, Physics::Optics, Spectral bands, Distributed Bragg reflector, Polarization (waves), Spectral line, Computer Science Applications, Education, Optics, Optoelectronics, Specular reflection, business, Gaas algaas, Quantum well
Abstract

Measurements of the optical reflection spectra from periodic structures with two quantum wells in the elementary cell have been done. The dependencies of the light reflection on the angle of the light incidence, polarization and temperature were studied. An analysis of the experimental data showed that the pattern with 60 cells is a good Bragg reflector with reflectivity more than 90% in the maximum of the spectral band.

Published
2016

6. Modeling of the optical properties of a two-dimensional system of small conductive particles

Author

A. A. Kondikov, V. V. Chaldyshev, Tigran A. Vartanyan, and P. A. Tonkaev

Subjects
History, Materials science, business.industry, Computer Science Applications, Education, Computational physics, Software, Reflection (mathematics), Optics, business, Absorption (electromagnetic radiation), Electrical conductor, Lattice model (physics), Transmittance spectra
Abstract

Software was developed for quick numerical calculations and graphic display of the absorption, reflection and transmittance spectra of two-dimensional systems of small conductive particles. It allowed us to make instant comparison of calculation results and experimental data. A lattice model was used to simulate nearly distributed particles, and the coherent-potential approximation was applied to obtain a solution to the problem of interacting particles. The Delphi programming environment was used.

Published
2016

7. Structural transformations in the low-temperature grown GaAs with superlattices of Sb and P δ-layers

Author

V. V. Preobrazhenskii, B. R. Semyagin, V. N. Nevedomsky, V. V. Chaldyshev, N.A. Bert, M. A. Yagovkina, M. A. Putyato, and M. V. Baidakova

Subjects
Diffraction, Chemistry, Annealing (metallurgy), Superlattice, Metals and Alloys, General Medicine, Reflectivity, General Biochemistry, Genetics and Molecular Biology, Atomic and Molecular Physics, and Optics, Structural transformation, Electronic, Optical and Magnetic Materials, Crystallography, Transmission electron microscopy, Materials Chemistry
Abstract

The structure of low-temperature grown GaAs with equi­distant δ-layers of Sb and P was studied by analysis of the X-ray curves, which was supported by optical absorption measurements and transmission electron microscopy. The simultaneous fitting of the X-ray reflectivity curve and diffraction ones for GaAs (004) and GaAs (115) crystallographic planes provided reliable information about the period of δ-layer superlattice, thickness of the Sb and P δ-layers, and amount of excess As. Variation of these parameters was documented when excess As precipitated into As nanoinclusions upon annealing. The Sb and P δ-layers impact differently on the As precipitation processes in low-temperature grown GaAs. The combination of Sb and P δ-layers appears to be an effective tool for spatial patterning of the nanoinclusion array and prevention of the defect formation under annealing.

Published
2012

8. Influence of the initial supersaturation of solute atoms on the size of nanoparticles grown by an Ostwald ripening mechanism

Author

Peter Werner, Nikolay Cherkashin, V. V. Preobrazhenskii, Mikhail A. Putyato, Alain Claverie, N.A. Bert, Caroline Bonafos, B. R. Semyagin, V. V. Chaldyshev, Matériaux et dispositifs pour l'Electronique et le Magnétisme ( CEMES-MEM ), Centre d'élaboration de matériaux et d'études structurales ( CEMES ), Institut National des Sciences Appliquées - Toulouse ( INSA Toulouse ), Institut National des Sciences Appliquées ( INSA ) -Institut National des Sciences Appliquées ( INSA ) -Université Paul Sabatier - Toulouse 3 ( UPS ) -Centre National de la Recherche Scientifique ( CNRS ) -Institut National des Sciences Appliquées - Toulouse ( INSA Toulouse ), Institut National des Sciences Appliquées ( INSA ) -Institut National des Sciences Appliquées ( INSA ) -Université Paul Sabatier - Toulouse 3 ( UPS ) -Centre National de la Recherche Scientifique ( CNRS ), Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] ( RAS ), Institute of Semiconductor Physics, Novosibirsk, Siberian Branch of the Russian Academy of Sciences ( SB RAS ), Max-Planck Institut für Mikrostrukturphysik, Max-Planck-Institut, Matériaux et dispositifs pour l'Electronique et le Magnétisme (CEMES-MEM), Centre d'élaboration de matériaux et d'études structurales (CEMES), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] (RAS), Siberian Branch of the Russian Academy of Sciences (SB RAS), Max-Planck-Institut für Mikrostrukturphysik (MPI-HALLE), Max-Planck-Gesellschaft, Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), and Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010302 applied physics, Ostwald ripening, Supersaturation, Materials science, Annealing (metallurgy), Precipitation (chemistry), Nucleation, General Physics and Astronomy, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Crystallography, symbols.namesake, Chemical physics, Phase (matter), 0103 physical sciences, Volume fraction, symbols, Particle size, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 0210 nano-technology, [ PHYS.COND ] Physics [physics]/Condensed Matter [cond-mat]
Abstract

International audience; We have designed a GaAs based structure in which the influence of the initial supersaturation of solute atoms, here As, on the nucleation and conservative growth of a precipitate phase during annealing can be studied. Size distributions and densities were extracted from transmission electron microscopy images under well defined and appropriate conditions, and the volume fraction that the precipitate phase occupies was deduced from these measurements for a variety of experimental conditions. We show that in the 0.06%–0.5% supersaturation range, the mean size of the precipitates obtained after annealing does not depend on the initial supersaturation of As atoms. On the other hand, the density of precipitates is proportional to this supersaturation. However, we observe that the increase of the precipitate volume fraction leads to a considerable broadening of the precipitate size distributions. The size invariance revealed here suggests that, for a volume fraction of less than 1%, the populations are in quasiequilibrium with the supersaturated matrix and that the growth is driven by the interchange of As atoms and vacancies between the precipitates and the matrix and not directly from one precipitate to the next. It can be inferred that the diffusion fields surrounding the precipitates do not overlap much during the growth although some deviation from the expected shape of the size distribution may reveal the limitations of the nonlocal mean-field approximation suggested here.

Published
2007

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