V. Chaldyshev | Ioffe Physical Technical Institute (original) (raw)

Papers by V. Chaldyshev

Research paper thumbnail of Gallium arsenide grown by molecular beam epitaxy at low temperatures: crystal structure, properties, superconductivity

Physics of the solid …, 1993

... BERNT NA (1) ; VEINGER AI (1) ; VILISOVA MD (1) ; GOLOSHCHAPOV SI (1) ; IVONIN IV (1) ; KOZYR... more ... BERNT NA (1) ; VEINGER AI (1) ; VILISOVA MD (1) ; GOLOSHCHAPOV SI (1) ; IVONIN IV (1) ; KOZYREV SV (1) ; KUNITSYN AE (1) ; LAVRENT'EVA LG (1) ; LUBYSHEV DI ; PREOBRAZHESKII VV ; SEMYAGIN BR ; TRET'YAKOV VV ; CHALDYSHEV VV ; YAKUBENYA MP ...

Research paper thumbnail of Bistability of charge accumulated in low-temperature-grown GaAs

Applied Physics Letters, 1998

Abstract Capacitance–voltage characteristics were studied at various temperatures for Schottky ba... more Abstract Capacitance–voltage characteristics were studied at various temperatures for Schottky barriers formed on n-GaAs/low-temperature-grown (LT)-GaAs/n-GaAs sandwich structures. Charge accumulation at deep traps in the LT-GaAs layer was observed. At room temperature, the C–V characteristics were found to be step-like with a wide plateau originated from emission of electrons accumulated in the LT-GaAs layer. At the temperature below 100 K, the electron emission from the LT-GaAs layer was completely suppressed. ...

Research paper thumbnail of Resonant Bragg structures based on III-nitrides

Journal of Materials Research, 2015

ABSTRACT We demonstrate a resonant Bragg structure formed by quasi-two-dimensional excitons in pe... more ABSTRACT We demonstrate a resonant Bragg structure formed by quasi-two-dimensional excitons in periodic systems of InGaN quantum wells (QWs) separated by GaN barriers. When the Bragg resonance and exciton-polariton resonance are tuned to each other, the medium exhibits an exciton-mediated resonantly enhanced optical Bragg reflection. The enhancement factor appeared to be largest for the system of 60 QWs. Owing to a high binding energy and oscillator strength of the excitons in InGaN QWs, the resonant enhancement was achieved at room temperature. The samples were grown by the metal-organic vapor-phase epitaxy (MOVPE) on GaN-on-sapphire templates. The most important technological problem of the developed structures is inhomogeneous broadening of the excitonic states due to nonuniform chemical composition of the QWs driven by InN-GaN phase separation trend. We addressed this problem by variation of the vapor pressure, growth rate, growth interactions, and admixing of hydrogen during the MOVPE. The lowest width of 74 meV at room temperature and 41 meV at 77 K was achieved for the excitonic emission line from a single InGaN QW.

Research paper thumbnail of Optical reflection and contactless electroreflection from GaAlAs layers with periodically arranged GaAs quantum wells

Research paper thumbnail of Capacitance study of electron traps in low-temperature-grown GaAs

Semiconductors, 2004

Electron traps in GaAs grown by MBE at temperatures of 200–300C (LT-GaAs) were studied. Capacitan... more Electron traps in GaAs grown by MBE at temperatures of 200–300C (LT-GaAs) were studied. Capacitance deep level transient spectroscopy (DLTS) was used to study the Schottky barrier on n-GaAs, whose space-charge region contained a built-in LT-GaAs layer ∼0.1 m thick. The size of arsenic clusters formed in LT-GaAs on annealing at 580C depended on the growth temperature. Two new types of electron traps were found in LT-GaAs layers grown at 200C and containing As clusters 6–8 nm in diameter. The activation energy of thermal electron emission from these traps was 0.47 and 0.59 eV, and their concentration was ∼1017 cm−3, which is comparable with the concentration of As clusters determined by transmission electron microscopy. In LT-GaAs samples that were grown at 300C and contained no arsenic clusters, the activation energy of traps was 0.61 eV. The interrelation between these electron levels and the system of As clusters and point defects in LT-GaAs is discussed.

Research paper thumbnail of A Study of Recombination Centers Related to As–Sb Nanoclusters in Low-Temperature Grown Gallium Arsenide

Semiconductors, 2005

Electronic traps in “low-temperature” GaAs (LT-GaAs) grown at 150°C were studied. The As-Sb clust... more Electronic traps in “low-temperature” GaAs (LT-GaAs) grown at 150°C were studied. The As-Sb clusters appearing in this material after annealing were located in a plane that contained a single Sb monolayer formed during growth. The diameter of the clusters was as large as 20 nm. For the purpose of measurement, Au-n-GaAs Schottky barriers were used, in which, for certain bias voltages, the space charge region enclosed the narrow LT-GaAs layer containing the plane of clusters. The bias-voltage dependence of the structure capacitance indicates that the majority of the electrons in this layer are captured by traps, whose energy level lies ∼0.5 eV below the bottom of the conduction band. The energy density of states at this energy is 1014 cm−2 eV−1, which sharply decreases towards the midgap. The existence of traps with activation energies of ∼0.5 eV for the thermal emission of electrons is confirmed by deep-level transient spectroscopy. The magnitude of the electroncapture cross section determined by this method is in the range 5 × 10−14−1 × 10−12 cm2. It is assumed that traps of this type are related to large As-Sb clusters.

Research paper thumbnail of Accumulation of majority charge carriers in GaAs layers containing arsenic nanoclusters

Semiconductors, 2000

Abstract The accumulation of electrons and holes in GaAs layers that contained As clusters and we... more Abstract The accumulation of electrons and holes in GaAs layers that contained As clusters and were sandwiched between n-and p-type buffer GaAs layers was revealed by capacitance-voltage measurements. As a result of majority-carrier accumulation, expansive depletion regions are formed in the adjoining buffer layers. Simulation of the capacitance-voltage characteristics, based on a numerical solution of the Poisson equation, shows that the accumulated charge density is∼ 110 12 cm− 2, which is comparable with the ...

Research paper thumbnail of Optical lattices of excitons in InGaN/GaN quantum well systems

Semiconductors

Optical lattices of excitons in periodic systems of InGaN quantum wells with GaN barriers are des... more Optical lattices of excitons in periodic systems of InGaN quantum wells with GaN barriers are designed, implemented, and investigated. Due to the collective interaction of quasi-two-dimensional excitons with light and a fairly high binding energy of excitons in GaN, optical Bragg reflection at room temperature is significantly enhanced. To increase the resonance optical response of the system, new structures with two quantum wells in a periodic supercell are designed and implemented. Resonance reflection of 40% at room temperatures for structures with 60 periods is demonstrated.

Research paper thumbnail of Structure Probed by Modulation Reflectance Spectroscopy

Second quantum state transition in GaAs/AlGaAs resonant Bragg structure probed by modulation refl... more Second quantum state transition in GaAs/AlGaAs resonant Bragg structure probed by modulation reflectance spectroscopy

Research paper thumbnail of Modulation optical spectroscopy of excitons in structures with GaAs multiple quantum wells separated by tunneling-nontransparent barriers

Semiconductors, 2007

Contactless optical electroreflectance measurements at different temperatures are used to study e... more Contactless optical electroreflectance measurements at different temperatures are used to study exciton states in a structure involving a periodic system of 36 GaAs quantum wells separated by tunneling-nontransparent AlGaAs barriers with thickness 104 nm. In the structure, the width of 32 of the quantum wells is 15 nm, while the width of the remaining four quantum wells, numbered 5, 14, 23, and 32, is 20 nm. The periodicity of the structure corresponds to the Bragg interference condition at the excitonic frequency in quantum wells at the angle of incidence of light ~43 °. From the quantitative analysis of the shape of the contactless electroreflectance line, the parameters of the exciton ground states and excited states are determined for both types of quantum wells. It is established that, for the system of four 20-nm-wide quantum wells separated by a distance of 830 nm, the size-quantization energy in the ground state is 8.4 ± 0.1 meV, and the parameter of broadening of the excitonic peak is 1.8 ± 0.1 meV at 17 K and increases with temperature up to 2.0 ± 0.1 meV at 80 K. For the system of 32 wells with the width 15 nm, the quantum confinement energy in the ground state is 14.9 ± 0.1 meV, and the parameter of broadening of the excitonic peak is 2.2 ± 0.1 and 2.6 ± 0.1 meV at 17 and 80 K, respectively. The possible causes of radiative and nonradiative broadening of exciton states in the systems are discussed.

Research paper thumbnail of Resonance Bragg structure with double InGaN quantum wells

Physics of the Solid State, 2013

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

Journal of Materials Science: Materials in Electronics, 2008

We studied optical reflection (OR) and contactless electroreflection (CER) from a periodic system... more 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.

Research paper thumbnail of Modulation optical spectroscopy of excitons in structures with GaAs multiple quantum wells separated by tunneling-nontransparent barriers

Semiconductors, 2007

Contactless optical electroreflectance measurements at different temperatures are used to study e... more Contactless optical electroreflectance measurements at different temperatures are used to study exciton states in a structure involving a periodic system of 36 GaAs quantum wells separated by tunneling-nontransparent AlGaAs barriers with thickness 104 nm. In the structure, the width of 32 of the quantum wells is 15 nm, while the width of the remaining four quantum wells, numbered 5, 14, 23, and 32, is 20 nm. The periodicity of the structure corresponds to the Bragg interference condition at the excitonic frequency in quantum wells at the angle of incidence of light ~43 °. From the quantitative analysis of the shape of the contactless electroreflectance line, the parameters of the exciton ground states and excited states are determined for both types of quantum wells. It is established that, for the system of four 20-nm-wide quantum wells separated by a distance of 830 nm, the size-quantization energy in the ground state is 8.4 ± 0.1 meV, and the parameter of broadening of the excitonic peak is 1.8 ± 0.1 meV at 17 K and increases with temperature up to 2.0 ± 0.1 meV at 80 K. For the system of 32 wells with the width 15 nm, the quantum confinement energy in the ground state is 14.9 ± 0.1 meV, and the parameter of broadening of the excitonic peak is 2.2 ± 0.1 and 2.6 ± 0.1 meV at 17 and 80 K, respectively. The possible causes of radiative and nonradiative broadening of exciton states in the systems are discussed.

Research paper thumbnail of Influence of the initial supersaturation of solute atoms on the size of nanoparticles grown by an Ostwald ripening mechanism

Journal of Applied Physics, 2007

We have designed a GaAs based structure in which the influence of the initial supersaturation of ... more 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 vacancies͒ 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.

Research paper thumbnail of Gallium arsenide grown by molecular beam epitaxy at low temperatures: crystal structure, properties, superconductivity

Physics of the solid …, 1993

... BERNT NA (1) ; VEINGER AI (1) ; VILISOVA MD (1) ; GOLOSHCHAPOV SI (1) ; IVONIN IV (1) ; KOZYR... more ... BERNT NA (1) ; VEINGER AI (1) ; VILISOVA MD (1) ; GOLOSHCHAPOV SI (1) ; IVONIN IV (1) ; KOZYREV SV (1) ; KUNITSYN AE (1) ; LAVRENT'EVA LG (1) ; LUBYSHEV DI ; PREOBRAZHESKII VV ; SEMYAGIN BR ; TRET'YAKOV VV ; CHALDYSHEV VV ; YAKUBENYA MP ...

Research paper thumbnail of Structural study of low-temperature grown superlattices of GaAs with delta-layers of Sb and P

Physica B: Condensed Matter, 2009

The structure of low-temperature grown superlattices of GaAs with delta-layers of Sb and P was st... more The structure of low-temperature grown superlattices of GaAs with delta-layers of Sb and P was studied by analysis of the X-ray diffraction curves, which was accompanied by optical absorption measurements and transmission electron microscopy. The obtained structural parameters included the periods of structure, thicknesses of the Sb and P d-layers, amount of excess As in the as-grown state. Variations of these parameters were documented when samples were annealed and the excess As transformed from antisite defects into As nanoinclusions.

Research paper thumbnail of Self-organization of InAs and As quantum dots in GaAs by a combined molecular beam epitaxy process

physica status solidi (c), 2000

ABSTRACT We show a possibility to self-organize In As semiconductor quantum dots (SQDs) and As se... more ABSTRACT We show a possibility to self-organize In As semiconductor quantum dots (SQDs) and As semimetal quantum dots (MQDs) in a close vicinity to each other in the GaAs matrix. For that we develop a combined process of the molecular beam epitaxy (MBE), in which self-organization of the In As SQDs was achieved in the Stranski-Krastanow mode, whereas self-organization of the As MQDs was realized by the low-temperature MBE with the subsequent anneal. [GRAPHICS] Bright-field cross-sectional TEM micrograph of a GaAs film with double layers of InAs SQDs and As MQDs in the low-temperature grown GaAs cap. g = 002. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Research paper thumbnail of Formation of dislocation defects in the process of burying of InAs quantum dots into GaAs

Semiconductors, 2009

Evidence given by electron microscopy of dislocation relaxation of stresses near InAs quantum dot... more Evidence given by electron microscopy of dislocation relaxation of stresses near InAs quantum dots buried into GaAs is presented. It was found that dislocation defects not emerging to the film surface are formed in some buried quantum dots. This suggests that stress relaxation occurs in the buried state of the quantum dot, rather than at the stage of the formation and growth of an InAs island on the GaAs surface. Models of internal dislocation relaxation of buried quantum dots are presented.

Research paper thumbnail of Two- and three-dimensional arrays of nanoscale as clusters in low-temperature grown GaAs

12th International Conference on Semiconducting and Insulating Materials, 2002. SIMC-XII-2002., 2002

ABSTRACT

Research paper thumbnail of Two-dimensional precipitation of As clusters due to indium delta-doping of GaAs films grown by molecular beam epitaxy at low temperature

Semiconductor Science and Technology, 1997

... Two-dimensional precipitation of As clusters due to indium delta-doping of GaAs films grown b... more ... Two-dimensional precipitation of As clusters due to indium delta-doping of GaAs films grown by molecular beam epitaxy at low temperature NA Bert†, VV Chaldyshev†, NN Faleev†, AE Kunitsyn†, DI Lubyshev‡, VV Preobrazhenskii‡, BR Semyagin‡ and VV Tret'yakov† ...

Research paper thumbnail of Gallium arsenide grown by molecular beam epitaxy at low temperatures: crystal structure, properties, superconductivity

Physics of the solid …, 1993

... BERNT NA (1) ; VEINGER AI (1) ; VILISOVA MD (1) ; GOLOSHCHAPOV SI (1) ; IVONIN IV (1) ; KOZYR... more ... BERNT NA (1) ; VEINGER AI (1) ; VILISOVA MD (1) ; GOLOSHCHAPOV SI (1) ; IVONIN IV (1) ; KOZYREV SV (1) ; KUNITSYN AE (1) ; LAVRENT'EVA LG (1) ; LUBYSHEV DI ; PREOBRAZHESKII VV ; SEMYAGIN BR ; TRET'YAKOV VV ; CHALDYSHEV VV ; YAKUBENYA MP ...

Research paper thumbnail of Bistability of charge accumulated in low-temperature-grown GaAs

Applied Physics Letters, 1998

Abstract Capacitance–voltage characteristics were studied at various temperatures for Schottky ba... more Abstract Capacitance–voltage characteristics were studied at various temperatures for Schottky barriers formed on n-GaAs/low-temperature-grown (LT)-GaAs/n-GaAs sandwich structures. Charge accumulation at deep traps in the LT-GaAs layer was observed. At room temperature, the C–V characteristics were found to be step-like with a wide plateau originated from emission of electrons accumulated in the LT-GaAs layer. At the temperature below 100 K, the electron emission from the LT-GaAs layer was completely suppressed. ...

Research paper thumbnail of Resonant Bragg structures based on III-nitrides

Journal of Materials Research, 2015

ABSTRACT We demonstrate a resonant Bragg structure formed by quasi-two-dimensional excitons in pe... more ABSTRACT We demonstrate a resonant Bragg structure formed by quasi-two-dimensional excitons in periodic systems of InGaN quantum wells (QWs) separated by GaN barriers. When the Bragg resonance and exciton-polariton resonance are tuned to each other, the medium exhibits an exciton-mediated resonantly enhanced optical Bragg reflection. The enhancement factor appeared to be largest for the system of 60 QWs. Owing to a high binding energy and oscillator strength of the excitons in InGaN QWs, the resonant enhancement was achieved at room temperature. The samples were grown by the metal-organic vapor-phase epitaxy (MOVPE) on GaN-on-sapphire templates. The most important technological problem of the developed structures is inhomogeneous broadening of the excitonic states due to nonuniform chemical composition of the QWs driven by InN-GaN phase separation trend. We addressed this problem by variation of the vapor pressure, growth rate, growth interactions, and admixing of hydrogen during the MOVPE. The lowest width of 74 meV at room temperature and 41 meV at 77 K was achieved for the excitonic emission line from a single InGaN QW.

Research paper thumbnail of Optical reflection and contactless electroreflection from GaAlAs layers with periodically arranged GaAs quantum wells

Research paper thumbnail of Capacitance study of electron traps in low-temperature-grown GaAs

Semiconductors, 2004

Electron traps in GaAs grown by MBE at temperatures of 200–300C (LT-GaAs) were studied. Capacitan... more Electron traps in GaAs grown by MBE at temperatures of 200–300C (LT-GaAs) were studied. Capacitance deep level transient spectroscopy (DLTS) was used to study the Schottky barrier on n-GaAs, whose space-charge region contained a built-in LT-GaAs layer ∼0.1 m thick. The size of arsenic clusters formed in LT-GaAs on annealing at 580C depended on the growth temperature. Two new types of electron traps were found in LT-GaAs layers grown at 200C and containing As clusters 6–8 nm in diameter. The activation energy of thermal electron emission from these traps was 0.47 and 0.59 eV, and their concentration was ∼1017 cm−3, which is comparable with the concentration of As clusters determined by transmission electron microscopy. In LT-GaAs samples that were grown at 300C and contained no arsenic clusters, the activation energy of traps was 0.61 eV. The interrelation between these electron levels and the system of As clusters and point defects in LT-GaAs is discussed.

Research paper thumbnail of A Study of Recombination Centers Related to As–Sb Nanoclusters in Low-Temperature Grown Gallium Arsenide

Semiconductors, 2005

Electronic traps in “low-temperature” GaAs (LT-GaAs) grown at 150°C were studied. The As-Sb clust... more Electronic traps in “low-temperature” GaAs (LT-GaAs) grown at 150°C were studied. The As-Sb clusters appearing in this material after annealing were located in a plane that contained a single Sb monolayer formed during growth. The diameter of the clusters was as large as 20 nm. For the purpose of measurement, Au-n-GaAs Schottky barriers were used, in which, for certain bias voltages, the space charge region enclosed the narrow LT-GaAs layer containing the plane of clusters. The bias-voltage dependence of the structure capacitance indicates that the majority of the electrons in this layer are captured by traps, whose energy level lies ∼0.5 eV below the bottom of the conduction band. The energy density of states at this energy is 1014 cm−2 eV−1, which sharply decreases towards the midgap. The existence of traps with activation energies of ∼0.5 eV for the thermal emission of electrons is confirmed by deep-level transient spectroscopy. The magnitude of the electroncapture cross section determined by this method is in the range 5 × 10−14−1 × 10−12 cm2. It is assumed that traps of this type are related to large As-Sb clusters.

Research paper thumbnail of Accumulation of majority charge carriers in GaAs layers containing arsenic nanoclusters

Semiconductors, 2000

Abstract The accumulation of electrons and holes in GaAs layers that contained As clusters and we... more Abstract The accumulation of electrons and holes in GaAs layers that contained As clusters and were sandwiched between n-and p-type buffer GaAs layers was revealed by capacitance-voltage measurements. As a result of majority-carrier accumulation, expansive depletion regions are formed in the adjoining buffer layers. Simulation of the capacitance-voltage characteristics, based on a numerical solution of the Poisson equation, shows that the accumulated charge density is∼ 110 12 cm− 2, which is comparable with the ...

Research paper thumbnail of Optical lattices of excitons in InGaN/GaN quantum well systems

Semiconductors

Optical lattices of excitons in periodic systems of InGaN quantum wells with GaN barriers are des... more Optical lattices of excitons in periodic systems of InGaN quantum wells with GaN barriers are designed, implemented, and investigated. Due to the collective interaction of quasi-two-dimensional excitons with light and a fairly high binding energy of excitons in GaN, optical Bragg reflection at room temperature is significantly enhanced. To increase the resonance optical response of the system, new structures with two quantum wells in a periodic supercell are designed and implemented. Resonance reflection of 40% at room temperatures for structures with 60 periods is demonstrated.

Research paper thumbnail of Structure Probed by Modulation Reflectance Spectroscopy

Second quantum state transition in GaAs/AlGaAs resonant Bragg structure probed by modulation refl... more Second quantum state transition in GaAs/AlGaAs resonant Bragg structure probed by modulation reflectance spectroscopy

Research paper thumbnail of Modulation optical spectroscopy of excitons in structures with GaAs multiple quantum wells separated by tunneling-nontransparent barriers

Semiconductors, 2007

Contactless optical electroreflectance measurements at different temperatures are used to study e... more Contactless optical electroreflectance measurements at different temperatures are used to study exciton states in a structure involving a periodic system of 36 GaAs quantum wells separated by tunneling-nontransparent AlGaAs barriers with thickness 104 nm. In the structure, the width of 32 of the quantum wells is 15 nm, while the width of the remaining four quantum wells, numbered 5, 14, 23, and 32, is 20 nm. The periodicity of the structure corresponds to the Bragg interference condition at the excitonic frequency in quantum wells at the angle of incidence of light ~43 °. From the quantitative analysis of the shape of the contactless electroreflectance line, the parameters of the exciton ground states and excited states are determined for both types of quantum wells. It is established that, for the system of four 20-nm-wide quantum wells separated by a distance of 830 nm, the size-quantization energy in the ground state is 8.4 ± 0.1 meV, and the parameter of broadening of the excitonic peak is 1.8 ± 0.1 meV at 17 K and increases with temperature up to 2.0 ± 0.1 meV at 80 K. For the system of 32 wells with the width 15 nm, the quantum confinement energy in the ground state is 14.9 ± 0.1 meV, and the parameter of broadening of the excitonic peak is 2.2 ± 0.1 and 2.6 ± 0.1 meV at 17 and 80 K, respectively. The possible causes of radiative and nonradiative broadening of exciton states in the systems are discussed.

Research paper thumbnail of Resonance Bragg structure with double InGaN quantum wells

Physics of the Solid State, 2013

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

Journal of Materials Science: Materials in Electronics, 2008

We studied optical reflection (OR) and contactless electroreflection (CER) from a periodic system... more 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.

Research paper thumbnail of Modulation optical spectroscopy of excitons in structures with GaAs multiple quantum wells separated by tunneling-nontransparent barriers

Semiconductors, 2007

Contactless optical electroreflectance measurements at different temperatures are used to study e... more Contactless optical electroreflectance measurements at different temperatures are used to study exciton states in a structure involving a periodic system of 36 GaAs quantum wells separated by tunneling-nontransparent AlGaAs barriers with thickness 104 nm. In the structure, the width of 32 of the quantum wells is 15 nm, while the width of the remaining four quantum wells, numbered 5, 14, 23, and 32, is 20 nm. The periodicity of the structure corresponds to the Bragg interference condition at the excitonic frequency in quantum wells at the angle of incidence of light ~43 °. From the quantitative analysis of the shape of the contactless electroreflectance line, the parameters of the exciton ground states and excited states are determined for both types of quantum wells. It is established that, for the system of four 20-nm-wide quantum wells separated by a distance of 830 nm, the size-quantization energy in the ground state is 8.4 ± 0.1 meV, and the parameter of broadening of the excitonic peak is 1.8 ± 0.1 meV at 17 K and increases with temperature up to 2.0 ± 0.1 meV at 80 K. For the system of 32 wells with the width 15 nm, the quantum confinement energy in the ground state is 14.9 ± 0.1 meV, and the parameter of broadening of the excitonic peak is 2.2 ± 0.1 and 2.6 ± 0.1 meV at 17 and 80 K, respectively. The possible causes of radiative and nonradiative broadening of exciton states in the systems are discussed.

Research paper thumbnail of Influence of the initial supersaturation of solute atoms on the size of nanoparticles grown by an Ostwald ripening mechanism

Journal of Applied Physics, 2007

We have designed a GaAs based structure in which the influence of the initial supersaturation of ... more 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 vacancies͒ 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.

Research paper thumbnail of Gallium arsenide grown by molecular beam epitaxy at low temperatures: crystal structure, properties, superconductivity

Physics of the solid …, 1993

... BERNT NA (1) ; VEINGER AI (1) ; VILISOVA MD (1) ; GOLOSHCHAPOV SI (1) ; IVONIN IV (1) ; KOZYR... more ... BERNT NA (1) ; VEINGER AI (1) ; VILISOVA MD (1) ; GOLOSHCHAPOV SI (1) ; IVONIN IV (1) ; KOZYREV SV (1) ; KUNITSYN AE (1) ; LAVRENT'EVA LG (1) ; LUBYSHEV DI ; PREOBRAZHESKII VV ; SEMYAGIN BR ; TRET'YAKOV VV ; CHALDYSHEV VV ; YAKUBENYA MP ...

Research paper thumbnail of Structural study of low-temperature grown superlattices of GaAs with delta-layers of Sb and P

Physica B: Condensed Matter, 2009

The structure of low-temperature grown superlattices of GaAs with delta-layers of Sb and P was st... more The structure of low-temperature grown superlattices of GaAs with delta-layers of Sb and P was studied by analysis of the X-ray diffraction curves, which was accompanied by optical absorption measurements and transmission electron microscopy. The obtained structural parameters included the periods of structure, thicknesses of the Sb and P d-layers, amount of excess As in the as-grown state. Variations of these parameters were documented when samples were annealed and the excess As transformed from antisite defects into As nanoinclusions.

Research paper thumbnail of Self-organization of InAs and As quantum dots in GaAs by a combined molecular beam epitaxy process

physica status solidi (c), 2000

ABSTRACT We show a possibility to self-organize In As semiconductor quantum dots (SQDs) and As se... more ABSTRACT We show a possibility to self-organize In As semiconductor quantum dots (SQDs) and As semimetal quantum dots (MQDs) in a close vicinity to each other in the GaAs matrix. For that we develop a combined process of the molecular beam epitaxy (MBE), in which self-organization of the In As SQDs was achieved in the Stranski-Krastanow mode, whereas self-organization of the As MQDs was realized by the low-temperature MBE with the subsequent anneal. [GRAPHICS] Bright-field cross-sectional TEM micrograph of a GaAs film with double layers of InAs SQDs and As MQDs in the low-temperature grown GaAs cap. g = 002. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Research paper thumbnail of Formation of dislocation defects in the process of burying of InAs quantum dots into GaAs

Semiconductors, 2009

Evidence given by electron microscopy of dislocation relaxation of stresses near InAs quantum dot... more Evidence given by electron microscopy of dislocation relaxation of stresses near InAs quantum dots buried into GaAs is presented. It was found that dislocation defects not emerging to the film surface are formed in some buried quantum dots. This suggests that stress relaxation occurs in the buried state of the quantum dot, rather than at the stage of the formation and growth of an InAs island on the GaAs surface. Models of internal dislocation relaxation of buried quantum dots are presented.

Research paper thumbnail of Two- and three-dimensional arrays of nanoscale as clusters in low-temperature grown GaAs

12th International Conference on Semiconducting and Insulating Materials, 2002. SIMC-XII-2002., 2002

ABSTRACT

Research paper thumbnail of Two-dimensional precipitation of As clusters due to indium delta-doping of GaAs films grown by molecular beam epitaxy at low temperature

Semiconductor Science and Technology, 1997

... Two-dimensional precipitation of As clusters due to indium delta-doping of GaAs films grown b... more ... Two-dimensional precipitation of As clusters due to indium delta-doping of GaAs films grown by molecular beam epitaxy at low temperature NA Bert†, VV Chaldyshev†, NN Faleev†, AE Kunitsyn†, DI Lubyshev‡, VV Preobrazhenskii‡, BR Semyagin‡ and VV Tret'yakov† ...