Physics and Astronomy › Atomic and Molecular Physics, and Optics

Semiconductor Quantum Structures and Devices

Works Count: 128242

Wikipedia

Description

This cluster of papers focuses on the physics and applications of quantum dot devices, semiconductor materials, and single-photon sources. It covers topics such as band parameters for III–V compound semiconductors, strong coupling in quantum dot–semiconductor microcavity systems, and the generation of entangled photons from single quantum dots. The research also delves into the electronic structure of quantum dots, electrically driven single-photon sources, and the development of near-optimal single-photon sources in the solid state.

Keywords

Quantum Dots; Semiconductor; Single-Photon Source; Excitons; Microcavity; Band Parameters; Entangled Photons; Optical Emission; Nanowires; Photovoltaics

Quantum States of Confined Carriers in Very Thin<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Al</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ga</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mi mathvariant="normal">As</mml:mi></mml:math>-GaAs…

1974-09-30

R. Dingle , W. Wiegmann , C. H. Henry

Quantum levels associated with the confinement of carriers in very thin, molecular-beam-grown ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$-GaAs-${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ heterostructures result in pronounced structure in the GaAs optical absorption spectrum. Up to eight resolved exciton transitions, … Quantum levels associated with the confinement of carriers in very thin, molecular-beam-grown ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$-GaAs-${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ heterostructures result in pronounced structure in the GaAs optical absorption spectrum. Up to eight resolved exciton transitions, associated with different bound-electron and bound-hole states, have been observed. The heterostructure behaves as a simple rectangular potential well with a depth of $\ensuremath{\approx}0.88\ensuremath{\Delta}{E}_{g}$ for confining electrons and $\ensuremath{\approx}0.12\ensuremath{\Delta}{E}_{g}$ for confining holes, where $\ensuremath{\Delta}{E}_{g}$ is the difference in the semiconductor energy gaps.

Quantum size effect in semiconductor microcrystals

1985-12-01

A. I. Ekimov , Al. L. Éfros , A. A. Onushchenko

Direct formation of quantum-sized dots from uniform coherent islands of InGaAs on GaAs surfaces

1993-12-06

D. Leonard , Mohan Krishnamurthy , C.M. Reaves +2 more

The 2D–3D growth mode transition during the initial stages of growth of highly strained InGaAs on GaAs is used to obtain quantum-sized dot structures. Transmission electron micrographs reveal that when … The 2D–3D growth mode transition during the initial stages of growth of highly strained InGaAs on GaAs is used to obtain quantum-sized dot structures. Transmission electron micrographs reveal that when the growth of In0.5Ga0.5As is interrupted exactly at the onset of this 2D–3D transition, dislocation-free islands (dots) of the InGaAs result. Size distributions indicate that these dots are ∼300 Å in diameter and remarkably uniform to within 10% of this average size. The areal dot densities can be varied between 109 and 1011 cm−2. The uniformity of the dot sizes is explained by a mechanism based on reduction in adatom attachment probabilities due to strain. We unambiguously demonstrate photoluminescence at ∼1.2 eV from these islands by comparing samples with and without dots. The luminescent intensities of the dots are greater than or equal to those of the underlying reference quantum wells.

Gain and the threshold of three-dimensional quantum-box lasers

1986-09-01

Masahiro Asada , Yasuyuki Miyamoto , Y. Suematsu

Gain and threshold current density are analyzed for quantum-box lasers where electrons are confined in quantum well three-dimensionally, based on the density-matrix theory of semiconductor lasers with relaxation broadening. The … Gain and threshold current density are analyzed for quantum-box lasers where electrons are confined in quantum well three-dimensionally, based on the density-matrix theory of semiconductor lasers with relaxation broadening. The electronic dipole moment and its polarization dependence are first analyzed, and it is shown that the gain becomes maximum when the electric field of light is parallel to the longest side of the quantum box. Calculated gain is about 10 times that of bulk crystal for 100 Å × 100 Å × 100 Å GaAs/Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.8</inf> Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</inf> As quantum box, and 15 times for Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</inf> In <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</inf> As/InP quantum box with the same size, respectively. The threshold current density are 45 A/cm 2 and 62 A/cm 2 for GRINSCH GaAs/(Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.8</inf> Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</inf> As-Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</inf> Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</inf> As) and Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</inf> In <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</inf> As/(Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.28</inf> In <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.72</inf> As <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</inf> P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</inf> -InP), respectively, where for the GaInAs/ GaInAsP/InP system the intervalence band absorption and nonradiative recombinations have been assumed to be the same as those obtained for bulk crystals experimentally. These results show the possibility of remarkable reduction in the laser threshold by the quantum-box structures.

Band structure of indium antimonide

1957-01-01

E. O. Kane

Linear and nonlinear optical properties of semiconductor quantum wells

1989-01-01

S. Schmitt‐Rink , D. S. Chemla , David A. B. Miller

Abstract In this article we review the experimental and theoretical investigations of the linear and nonlinear optical properties of semiconductor quantum well structures, including the effects of electrostatic fields, extrinsic … Abstract In this article we review the experimental and theoretical investigations of the linear and nonlinear optical properties of semiconductor quantum well structures, including the effects of electrostatic fields, extrinsic carriers and real or virtual photocarriers.

Self-Organization in Growth of Quantum Dot Superlattices

1996-03-04

J. Tersoff , Christian Teichert , M. G. Lagally

We investigate the growth of multilayer arrays of coherently strained islands, which may serve as ``quantum dots'' in electronic devices. A simple model reproduces the observed vertical correlation between islands … We investigate the growth of multilayer arrays of coherently strained islands, which may serve as ``quantum dots'' in electronic devices. A simple model reproduces the observed vertical correlation between islands in successive layers. However, the arrangement of islands is not simply repeated from layer to layer. Instead, the island size and spacing grow progressively more uniform. In effect, the structure ``self-organizes'' into a more regular three-dimensional arrangement, providing a possible route to obtain the size uniformity needed for electronic applications of quantum dot arrays.

Chemical potential dependence of defect formation energies in GaAs: Application to Ga self-diffusion

1991-10-01

Shengbai Zhang , John E. Northrup

We calculate absolute formation energies of native defects in GaAs. The formation energy and hence the equilibrium concentration of the defects depends strongly on the atomic chemical potentials of As … We calculate absolute formation energies of native defects in GaAs. The formation energy and hence the equilibrium concentration of the defects depends strongly on the atomic chemical potentials of As and Ga as well as the electron chemical potential. For example, the Ga vacancy concentration changes by more than ten orders of magnitude as the chemical potentials of As and Ga vary over the thermodynamically allowed range. This result indicates that the rate of self-diffusion depends strongly on the surface-annealing conditions.

Making Nonmagnetic Semiconductors Ferromagnetic

1998-08-14

Hideo Ohno

REVIEW Semiconductor devices generally take advantage of the charge of electrons, whereas magnetic materials are used for recording information involving electron spin. To make use of both charge and spin … REVIEW Semiconductor devices generally take advantage of the charge of electrons, whereas magnetic materials are used for recording information involving electron spin. To make use of both charge and spin of electrons in semiconductors, a high concentration of magnetic elements can be introduced in nonmagnetic III-V semiconductors currently in use for devices. Low solubility of magnetic elements was overcome by low-temperature nonequilibrium molecular beam epitaxial growth, and ferromagnetic (Ga,Mn)As was realized. Magnetotransport measurements revealed that the magnetic transition temperature can be as high as 110 kelvin. The origin of the ferromagnetic interaction is discussed. Multilayer heterostructures including resonant tunneling diodes (RTDs) have also successfully been fabricated. The magnetic coupling between two ferromagnetic (Ga,Mn)As films separated by a nonmagnetic layer indicated the critical role of the holes in the magnetic coupling. The magnetic coupling in all semiconductor ferromagnetic/nonmagnetic layered structures, together with the possibility of spin filtering in RTDs, shows the potential of the present material system for exploring new physics and for developing new functionality toward future electronics.

Optical properties of intrinsic silicon at 300 K

1995-01-01

Martin A. Green , Mark J. Keevers

Abstract An updated tabulation is presented of the optical properties of intrinsic silicon relevant to solar cell calculations. the absorption coeficient, refractive index and extinction coeficient at 300 K are … Abstract An updated tabulation is presented of the optical properties of intrinsic silicon relevant to solar cell calculations. the absorption coeficient, refractive index and extinction coeficient at 300 K are tabulated over the 0.25‐1.45 μm wavelength range at 0.01 μm intervals.

A Quantum Dot Single-Photon Turnstile Device

2000-12-22

Peter Michler , Alper Kıraz , Christoph Becher +5 more

Quantum communication relies on the availability of light pulses with strong quantum correlations among photons. An example of such an optical source is a single-photon pulse with a vanishing probability … Quantum communication relies on the availability of light pulses with strong quantum correlations among photons. An example of such an optical source is a single-photon pulse with a vanishing probability for detecting two or more photons. Using pulsed laser excitation of a single quantum dot, a single-photon turnstile device that generates a train of single-photon pulses was demonstrated. For a spectrally isolated quantum dot, nearly 100% of the excitation pulses lead to emission of a single photon, yielding an ideal single-photon source.

Vertically Self-Organized InAs Quantum Box Islands on GaAs(100)

1995-09-25

Qianghua Xie , A. Madhukar , Ping Chen +1 more

Coherent InAs islands separated by GaAs spacer layers are shown to exhibit self-organized growth along the vertical (i.e., growth) direction. The driving force for such vertically self-organized growth is shown … Coherent InAs islands separated by GaAs spacer layers are shown to exhibit self-organized growth along the vertical (i.e., growth) direction. The driving force for such vertically self-organized growth is shown to be the interacting strain fields induced by the islands which give rise to a preferred direction for In migration. A model analysis accounting for the mechanochemical surface diffusion gives an island average size and average separation dependent characteristic spacer layer thickness ${z}_{0}$ below which a vertically self-organized growth occurs.

Temperature dependence of semiconductor band gaps

1991-06-24

K.P. O’Donnell , X. Chen

The application of a simple three-parameter fit to the temperature dependence of semiconductor band gaps is justified on both practical and theoretical grounds. In all trials the fit is numerically … The application of a simple three-parameter fit to the temperature dependence of semiconductor band gaps is justified on both practical and theoretical grounds. In all trials the fit is numerically better than that obtained using the widely quoted Varshni equation. The formula is shown to be compatible with reasonable assumptions about the influence of phonons on the band-gap energy. Approximate analytical expressions are derived for the entropy and enthalpy of formation of electron-hole pairs in semiconductors.

Band parameters for III–V compound semiconductors and their alloys

2001-06-01

I. Vurgaftman , J. R. Meyer , L. R. Ram‐Mohan

We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, … We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

Magnetotransport properties ofp-type (In,Mn)As diluted magnetic III-V semiconductors

1992-04-27

Hideo Ohno , H. Munekata , T. Penney +2 more

Magnetotransport properties of p-type (In,Mn)As, a new diluted magnetic semiconductor based on a III-V semiconductor, are studied. The interaction between the holes and the Mn 3d spins is manifested in … Magnetotransport properties of p-type (In,Mn)As, a new diluted magnetic semiconductor based on a III-V semiconductor, are studied. The interaction between the holes and the Mn 3d spins is manifested in the anomalous Hall effect, which dominates the Hall resistivity from low temperature (0.4 K) to nearly room temperature, and in the formation of partial ferromagnetic order below 7.5 K, which is a cooperative phenomenon related to carrier localization. The coexistence of remanent magnetization and unsaturated spins as well as the large negative magnetoresistance at low temperatures is explained by the formation of large bound magnetic polarons.

Quantum Theory of the Optical and Electronic Properties of Semiconductors

1994-02-01

Hartmut Haug , S. W. Koch , L. V. Keldysh

This revised second edition on the Quantum Theory of the Optical and Electronic Properties of Semiconductors presents the basic elements needed to understand and engage in research in semiconductor physics. … This revised second edition on the Quantum Theory of the Optical and Electronic Properties of Semiconductors presents the basic elements needed to understand and engage in research in semiconductor physics. In this revised second edition misprints are corrected and some new and more detailed material is added. In order to treat the valence-band structure of semiconductors, an introduction to the k.p. theory and the related description in terms of the Luttinger Hamiltonian is included. An introductory chapter on mesoscopic semiconductor structures discussing the modifications of the envelope function approximation caused by the spatial quantum confinement is also included. Many results are developed in parallel first for bulk material, and then for quasi-two-dimensional quantum wells, and for quasi-one-dimensional quantum wires. Semiconductor quantum dots are treated in a separate chapter. The discussion of time-dependent and coherent phenomena in semiconductors has been considerably extended by including a section dealing with the theoretical description of photon echoes in semiconductors. A new chapter on magneto-absorption has been added, in which magneto-excitons and magneto-plasmas in two-dimensional systems are discussed. The chapter on electron kinetics due to the interaction with longitudinal-optical phonons has been extended. The material is presented in sufficient detail for graduate students and researchers who have a general background in quantum mechanics, and is aimed at solid state physicists, engineers, materials and optical scientists.

GaAs, AlAs, and AlxGa1−xAs: Material parameters for use in research and device applications

1985-08-01

Sadao Adachi

The AlxGa1−xAs/GaAs heterostructure system is potentially useful material for high-speed digital, high-frequency microwave, and electro-optic device applications. Even though the basic AlxGa1−xAs/GaAs heterostructure concepts are understood at this time, some … The AlxGa1−xAs/GaAs heterostructure system is potentially useful material for high-speed digital, high-frequency microwave, and electro-optic device applications. Even though the basic AlxGa1−xAs/GaAs heterostructure concepts are understood at this time, some practical device parameters in this system have been hampered by a lack of definite knowledge of many material parameters. Recently, Blakemore has presented numerical and graphical information about many of the physical and electronic properties of GaAs [J. S. Blakemore, J. Appl. Phys. 53, R123 (1982)]. The purpose of this review is (i) to obtain and clarify all the various material parameters of AlxGa1−xAs alloy from a systematic point of view, and (ii) to present key properties of the material parameters for a variety of research works and device applications. A complete set of material parameters are considered in this review for GaAs, AlAs, and AlxGa1−xAs alloys. The model used is based on an interpolation scheme and, therefore, necessitates known values of the parameters for the related binaries (GaAs and AlAs). The material parameters and properties considered in the present review can be classified into sixteen groups: (1) lattice constant and crystal density, (2) melting point, (3) thermal expansion coefficient, (4) lattice dynamic properties, (5) lattice thermal properties, (6) electronic-band structure, (7) external perturbation effects on the band-gap energy, (8) effective mass, (9) deformation potential, (10) static and high-frequency dielectric constants, (11) magnetic susceptibility, (12) piezoelectric constant, (13) Fröhlich coupling parameter, (14) electron transport properties, (15) optical properties, and (16) photoelastic properties. Of particular interest is the deviation of material parameters from linearity with respect to the AlAs mole fraction x. Some material parameters, such as lattice constant, crystal density, thermal expansion coefficient, dielectric constant, and elastic constant, obey Vegard’s rule well. Other parameters, e.g., electronic-band energy, lattice vibration (phonon) energy, Debye temperature, and impurity ionization energy, exhibit quadratic dependence upon the AlAs mole fraction. However, some kinds of the material parameters, e.g., lattice thermal conductivity, exhibit very strong nonlinearity with respect to x, which arises from the effects of alloy disorder. It is found that the present model provides generally acceptable parameters in good agreement with the existing experimental data. A detailed discussion is also given of the acceptability of such interpolated parameters from an aspect of solid-state physics. Key properties of the material parameters for use in research work and a variety of AlxGa1−xAs/GaAs device applications are also discussed in detail.

Linewidth dependence of radiative exciton lifetimes in quantum wells

1987-11-16

Jochen Feldmann , G. Peter , E. O. Göbel +4 more

The fundamental relationship between radiative lifetime and spectral linewidth of free excitons is demonstrated theoretically and experimentally for quasi 2D excitons in GaAs/AlGaAs quantum wells.Received 24 August 1987DOI:https://doi.org/10.1103/PhysRevLett.59.2337©1987 American Physical … The fundamental relationship between radiative lifetime and spectral linewidth of free excitons is demonstrated theoretically and experimentally for quasi 2D excitons in GaAs/AlGaAs quantum wells.Received 24 August 1987DOI:https://doi.org/10.1103/PhysRevLett.59.2337©1987 American Physical Society

Defects in epitaxial multilayers I. Misfit dislocations

1974-12-01

Jacqueline M. Matthews

Photoluminescence of Single InAs Quantum Dots Obtained by Self-Organized Growth on GaAs

1994-08-01

J. Y. Marzin , Jean‐Michel Gérard , A. Izraël +2 more

We present photoluminescence data on InAs quantum dots grown by molecular beam epitaxy on GaAs. Through the reduction of the number of emitting dots in small mesa structures, we evidence … We present photoluminescence data on InAs quantum dots grown by molecular beam epitaxy on GaAs. Through the reduction of the number of emitting dots in small mesa structures, we evidence narrow lines in the spectra, each associated with a single InAs dot. Beyond the statistical analysis allowed by this technique, our results indicate short capture and relaxation times into the dots. This approach opens the route towards the detailed optical study of high quality easily fabricated single semiconductor quantum dots.

Kinetic pathway in Stranski-Krastanov growth of Ge on Si(001)

1990-08-20

Y. W. Mo , D. E. Savage , B. S. Swartzentruber +1 more

The transition from 2D to 3D growth of Ge on Si(001) has been investigated with scanning tunneling microscopy. A metastable 3D cluster phase with well-defined structure and shape is found. … The transition from 2D to 3D growth of Ge on Si(001) has been investigated with scanning tunneling microscopy. A metastable 3D cluster phase with well-defined structure and shape is found. The clusters have a {105} facet structure. Results suggest that these clusters define the kinetic path for formation of ``macroscopic'' Ge islands.

Electric field dependence of optical absorption near the band gap of quantum-well structures

1985-07-15

David A. B. Miller , D. S. Chemla , T. C. Damen +4 more

We report experiments and theory on the effects of electric fields on the optical absorption near the band edge in GaAs/AlGaAs quantum-well structures. We find distinct physical effects for fields … We report experiments and theory on the effects of electric fields on the optical absorption near the band edge in GaAs/AlGaAs quantum-well structures. We find distinct physical effects for fields parallel and perpendicular to the quantum-well layers. In both cases, we observe large changes in the absorption near the exciton peaks. In the parallel-field case, the excitons broaden with field, disappearing at fields \ensuremath{\sim}${10}^{4}$ V/cm; this behavior is in qualitative agreement with previous theory and in order-of-magnitude agreement with direct theoretical calculations of field ionization rates reported in this paper. This behavior is also qualitatively similar to that seen with three-dimensional semiconductors. For the perpendicular-field case, we see shifts of the exciton peaks to lower energies by up to 2.5 times the zero-field binding energy with the excitons remaining resolved at up to \ensuremath{\sim}${10}^{5}$ V/cm: This behavior is qualitatively different from that of bulk semiconductors and is explained through a mechanism previously briefly described by us [D. A. B. Miller et al., Phys. Rev. Lett. 53, 2173 (1984)] called the quantum-confined Stark effect. In this mechanism the quantum confinement of carriers inhibits the exciton field ionization. To support this mechanism we present detailed calculations of the shift of exciton peaks including (i) exact solutions for single particles in infinite wells, (ii) tunneling resonance calculations for finite wells, and (iii) variational calculations of exciton binding energy in a field. We also calculate the tunneling lifetimes of particles in the wells to check the inhibition of field ionization. The calculations are performed using both the 85:15 split of band-gap discontinuity between conduction and valence bands and the recently proposed 57:43 split. Although the detailed calculations differ in the two cases, the overall shift of the exciton peaks is not very sensitive to split ratio. We find excellent agreement with experiment with no fitted parameters.

Resonant tunneling in semiconductor double barriers

1974-06-15

L. L. Chang , L. Esaki , Raphael Tsu

Resonant tunneling of electrons has been observed in double-barrier structures having a thin GaAs sandwiched between two GaAlas barriers. The resonance manifests itself as peaks or humps in the tunneling … Resonant tunneling of electrons has been observed in double-barrier structures having a thin GaAs sandwiched between two GaAlas barriers. The resonance manifests itself as peaks or humps in the tunneling current at voltages near the quasistationary states of the potential well. The structures have been fabricated by molecular beam epitaxy which produces extremely smooth films and interfaces.

Theory of the linear and nonlinear optical properties of semiconductor microcrystallites

1987-05-15

S. Schmitt‐Rink , David A. B. Miller , D. S. Chemla

We analyze theoretically the optical properties of ideal semiconductor crystallites so small that they show quantum confinement in all three dimensions [quantum dots (QD's)]. In the limit of a QD … We analyze theoretically the optical properties of ideal semiconductor crystallites so small that they show quantum confinement in all three dimensions [quantum dots (QD's)]. In the limit of a QD much smaller than the bulk exciton size, the linear spectrum will be a series of lines, and we consider the phonon broadening of these lines. The lowest interband transition will saturate like a two-level system, without exchange and Coulomb screening. Depending on the broadening, the absorption and the changes in absorption and refractive index resulting from saturation can become very large, and the local-field effects can become so strong as to give optical bistability without external feedback. The small QD limit is more readily achieved with narrow-band-gap semiconductors.

GaInNAs: A Novel Material for Long-Wavelength-Range Laser Diodes with Excellent High-Temperature Performance

1996-02-01

Masahiko Kondow , K. Uomi , Atsuko Niwa +3 more

We propose a novel material, GaInNAs, that can be formed on GaAs to drastically improve the temperature characteristics ( T 0 ) in long-wavelength-range laser diodes. The feasibility of our … We propose a novel material, GaInNAs, that can be formed on GaAs to drastically improve the temperature characteristics ( T 0 ) in long-wavelength-range laser diodes. The feasibility of our proposal is demonstrated experimentally.

Electronic and optical properties of strained quantum dots modeled by 8-band k⋅p theory

1999-02-15

O. Stier , Marius Grundmann , D. Bimberg

We present a systematic investigation of the elastic, electronic, and linear optical properties of quantum dot double heterostructures in the frame of eight-band $\mathbf{k}\ensuremath{\cdot}\mathbf{p}$ theory. Numerical results for the model … We present a systematic investigation of the elastic, electronic, and linear optical properties of quantum dot double heterostructures in the frame of eight-band $\mathbf{k}\ensuremath{\cdot}\mathbf{p}$ theory. Numerical results for the model system of capped pyramid shaped InAs quantum dots in GaAs (001) with ${101}$ facets are presented. Electron and hole levels, dipole transition energies, oscillator strengths, and polarizations for both electron-hole and electron-electron transitions, as well as the exciton ground-state binding energy and the electron ground-state Coulomb charging energy are calculated. The dependence of all these properties on the dot size is investigated for base widths between 10 and $20$ nm. Results for two different approaches to model strain, continuum elasticity theory, and the Keatings valence force field model in the linearized version of Kane, are compared to each other.

Band-Edge Electroabsorption in Quantum Well Structures: The Quantum-Confined Stark Effect

1984-11-26

David A. B. Miller , D. S. Chemla , T. C. Damen +4 more

We present theory and extended experimental results for the large shift in optical absorption in GaAs-AlGaAs quantum well structures with electric field perpendicular to the layers. In contrast to the … We present theory and extended experimental results for the large shift in optical absorption in GaAs-AlGaAs quantum well structures with electric field perpendicular to the layers. In contrast to the Stark effect on atoms or on excitons in bulk semiconductors, the exciton resonances remain resolved even for shifts much larger than the zero-field binding energy and fields > 50 times the classical ionization field. The model explains these results as a consequence of the quantum confinement of carriers.

InAs/GaAs pyramidal quantum dots: Strain distribution, optical phonons, and electronic structure

1995-10-15

Marius Grundmann , O. Stier , D. Bimberg

The strain distribution in and around pyramidal InAs/GaAs quantum dots (QD's) on a thin wetting layer fabricated recently with molecular-beam epitaxy, is simulated numerically. For comparison analytical solutions for the … The strain distribution in and around pyramidal InAs/GaAs quantum dots (QD's) on a thin wetting layer fabricated recently with molecular-beam epitaxy, is simulated numerically. For comparison analytical solutions for the strain distribution in and around a pseudomorphic slab, cylinder, and sphere are given for isotropic materials, representing a guideline for the understanding of strain distribution in two-, one-, and zero-dimensional pseudomorphic nanostructures. For the pyramidal dots we find that the hydrostatic strain is mostly confined in the QD; in contrast part of the anisotropic strain is transferred from the QD into the barrier. The optical-phonon energies in the QD are estimated and agree perfectly with recent experimental findings. From the variation of the strain tensor the local band-gap modification is calculated. Piezoelectric effects are additionally taken into account. The three-dimensional effective-mass single-particle Schr\"odinger equation is solved for electrons and holes using the realistic confinement potentials. Since the QD's are in the strong confinement regime, the Coulomb interaction can be treated as a perturbation. The thus obtained electronic structure agrees with luminescence data. Additionally AlAs barriers are considered.

The Theory ofp-nJunctions in Semiconductors andp-nJunction Transistors

1949-07-01

W. Shockley

In a single crystal of semiconductor the impurity concentration may vary from p-type to n-type producing a mechanically continuous rectifying junction. The theory of potential distribution and rectification for p-n … In a single crystal of semiconductor the impurity concentration may vary from p-type to n-type producing a mechanically continuous rectifying junction. The theory of potential distribution and rectification for p-n junctions is developed with emphasis on germanium. The currents across the junction are carried by the diffusion of holes in n-type material and electrons in p-type material, resulting in an admittance for a simple case varying as (1 + iωτ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> ) 1/2 where τ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> is the lifetime of a hole in the n-region. Contact potentials across p-n junctions, carrying no current, may develop when hole or electron injection occurs. The principles and theory of a p-n-p transistor are described.

Optical Absorption of Gallium Arsenide between 0.6 and 2.75 eV

1962-08-01

M. D. Sturge

The optical absorption coefficient of high-resistivity gallium arsenide has been measured over the range of photon energy 0.6 to 2.75 eV, at temperatures from 10 to 294\ifmmode^\circ\else\textdegree\fi{}K. The main absorption … The optical absorption coefficient of high-resistivity gallium arsenide has been measured over the range of photon energy 0.6 to 2.75 eV, at temperatures from 10 to 294\ifmmode^\circ\else\textdegree\fi{}K. The main absorption edge shows a sharp peak due to the formation of excitons. The energy gap and exciton binding energy are deduced from the shape of the absorption curve above the edge. Their values at 21\ifmmode^\circ\else\textdegree\fi{}K are 1.521 and 0.0034 eV, respectively. Absorption from the split-off valence band is observed, the spin-orbit splitting being 0.35 eV at the center of the zone. The exciton line shows unexplained structure on the low-energy side. Application of a stress splits the exciton line by 12 eV per unit [111] shear, and shifts it by -10 eV per unit dilation. Absorption due to the ionization of deep-lying impurity levels is observed, with thresholds at 0.70, 0.49, and 0.27 eV from the main absorption edge.

Fine structure of neutral and charged excitons in self-assembled In(Ga)As/(Al)GaAs quantum dots

2002-05-07

M. Bayer , G. Ortner , O. Stern +7 more

The fine structure of excitons is studied by magnetophotoluminescence spectroscopy of single self-assembled In(Ga)As/(Al)GaAs quantum dots. Both strength and orientation of the magnetic field are varied. In a combination with … The fine structure of excitons is studied by magnetophotoluminescence spectroscopy of single self-assembled In(Ga)As/(Al)GaAs quantum dots. Both strength and orientation of the magnetic field are varied. In a combination with a detailed theoretical analysis, these studies allow us to develop a comprehensive picture of the exciton fine structure. Symmetry of the dot structures as well as its breaking cause characteristic features in the optical spectra, which are determined by the electron-hole exchange and the Zeeman interaction of the carriers. The symmetry breaking is either inherent to the dot due to geometry asymmetries, or it can be obtained by applying a magnetic field with an orientation different from the dot symmetry axis. From data on spin splitting and on polarization of the emission we can identify neutral as well as charged exciton complexes. For dots with weakly broken symmetry, the angular momentum of the neutral exciton is no longer a good quantum number and the exchange interaction lifts degeneracies within the fine-structure manifold. The symmetry can be restored by a magnetic field due to the comparatively strong Zeeman interactions of electron and hole. For dots with a strongly broken symmetry, bright and dark excitons undergo a strong hybridization, as evidenced by pronounced anticrossings when states within the manifold are brought into resonance. The fine structure can no longer be described within the frame developed for structures of higher dimensionality. In particular, the hybridization cannot be broken magnetically. For charged excitons, the exchange interaction vanishes, demonstrating that the exchange splitting of a neutral exciton can be switched off by injecting an additional carrier.

Electron mobilities in modulation-doped semiconductor heterojunction superlattices

1978-10-01

R. Dingle , H. L. Störmer , A. C. Gossard +1 more

GaAs-AlxGa1−xAs superlattice structures in which electron mobilities exceed those of otherwise equivalent epitaxial GaAs as well as the Brooks-Herring predictions near room temperature and at very low temperatures are reported. … GaAs-AlxGa1−xAs superlattice structures in which electron mobilities exceed those of otherwise equivalent epitaxial GaAs as well as the Brooks-Herring predictions near room temperature and at very low temperatures are reported. This new behavior is achieved via a modulation-doping technique that spatially separates conduction electrons and their parent donor impurity atoms, thereby reducing the influence of ionized and neutral impurity scattering on the electron motion.

View PDF Chat

Anomalous Optical Absorption Limit in InSb

1954-02-01

Elias Burstein

Phase noise in oscillators: a unifying theory and numerical methods for characterization

2000-05-01

Alper Demir , A. Mehrotra , Jaijeet Roychowdhury

Phase noise is a topic of theoretical and practical interest in electronic circuits, as well as in other fields, such as optics. Although progress has been made in understanding the … Phase noise is a topic of theoretical and practical interest in electronic circuits, as well as in other fields, such as optics. Although progress has been made in understanding the phenomenon, there still remain significant gaps, both in its fundamental theory and in numerical techniques for its characterization. In this paper, we develop a solid foundation for phase noise that is valid for any oscillator, regardless of operating mechanism. We establish novel results about the dynamics of stable nonlinear oscillators in the presence of perturbations, both deterministic and random. We obtain an exact nonlinear equation for phase error, which we solve without approximations for random perturbations. This leads us to a precise characterization of timing jitter and spectral dispersion, for computing of which we have developed efficient numerical methods. We demonstrate our techniques on a variety of practical electrical oscillators and obtain good matches with measurements, even at frequencies close to the carrier, where previous techniques break down. Our methods are more than three orders of magnitude faster than the brute-force Monte Carlo approach, which is the only previously available technique that can predict phase noise correctly.

Resonant tunneling through quantum wells at frequencies up to 2.5 THz

1983-09-15

T. C. L. G. Sollner , W. D. Goodhue , P. E. Tannenwald +2 more

Resonant tunneling through a single quantum well of GaAs has been observed. The current singularity and negative resistance region are dramatically improved over previous results, and detecting and mixing have … Resonant tunneling through a single quantum well of GaAs has been observed. The current singularity and negative resistance region are dramatically improved over previous results, and detecting and mixing have been carried out at frequencies as high as 2.5 THz. Resonant tunneling features are visible in the conductance-voltage curve at room temperature and become quite pronounced in the I-V curves at low temperature. The high-frequency results, measured with far IR lasers, prove that the charge transport is faster than about 10−13 s. It may now be possible to construct practical nonlinear devices using quantum wells at millimeter and submillimeter wavelengths.

View PDF Chat

Electrically Driven Single-Photon Source

2002-01-04

Zhiliang Yuan , Beata Kardynał , R. M. Stevenson +6 more

Electroluminescence from a single quantum dot within the intrinsic region of a p-i-n junction is shown to act as an electrically driven single-photon source. At low injection currents, the dot … Electroluminescence from a single quantum dot within the intrinsic region of a p-i-n junction is shown to act as an electrically driven single-photon source. At low injection currents, the dot electroluminescence spectrum reveals a single sharp line due to exciton recombination, while another line due to the biexciton emerges at higher currents. The second-order correlation function of the diode displays anti-bunching under a continuous drive current. Single-photon emission is stimulated by subnanosecond voltage pulses. These results suggest that semiconductor technology can be used to mass-produce a single-photon source for applications in quantum information technology.

View PDF Chat

Quantum Theory of Cyclotron Resonance in Semiconductors: General Theory

1956-05-15

J. M. Luttinger

The most general form of the Hamiltonian of an electron or hole in a semiconductor such as Si or Ge, in the presence of an external homogeneous magnetic field, is … The most general form of the Hamiltonian of an electron or hole in a semiconductor such as Si or Ge, in the presence of an external homogeneous magnetic field, is given. Two methods of obtaining the corresponding energy levels are discussed. The first should yield very accurate values for the magnetic field in the (111) direction for either Si or Ge. The second is a perturbation method and is expected to give good results only for Ge.

Intensity of Optical Absorption by Excitons

1957-12-15

R. J. Elliott

The intensity of optical absorption close to the edge in semiconductors is examined using band theory together with the effective-mass approximation for the excitons. Direct transitions which occur when the … The intensity of optical absorption close to the edge in semiconductors is examined using band theory together with the effective-mass approximation for the excitons. Direct transitions which occur when the band extrema on either side of the forbidden gap are at the same K, give a line spectrum and a continuous absorption of characteristically different form and intensity, according as transitions between band states at the extrema are allowed or forbidden. If the extrema are at different K values, indirect transitions involving phonons occur, giving absorption proportional to ${(\ensuremath{\Delta}E)}^{\frac{1}{2}}$ for each exciton band, and to ${(\ensuremath{\Delta}E)}^{2}$ for the continuum. The experimental results on ${\mathrm{Cu}}_{2}$O and Ge are in good qualitative agreement with direct forbidden and indirect transitions, respectively.

Ab initiocalculation of phonon dispersions in semiconductors

1991-03-15

Paolo Giannozzi , Stefano de Gironcoli , P. Pavone +1 more

The density-functional linear-response approach to lattice-dynamical calculations in semiconductors is presented in full detail. As an application, we calculate complete phonon dispersions for the elemental semiconductors Si and Ge, and … The density-functional linear-response approach to lattice-dynamical calculations in semiconductors is presented in full detail. As an application, we calculate complete phonon dispersions for the elemental semiconductors Si and Ge, and for the III-V semiconductor compounds GaAs, AlAs, GaSb, and AlSb. Our results are in excellent agreement with experiments where available, and provide predictions where they are not. As a byproduct, we obtain real-space interatomic force constants for these materials, which are useful both for interpolating the dynamical matrices through the Brillouin zone, and as ingredients of approximate calculations for mixed systems such as alloys and microstructures. The possibility of studying these systems using the force constants of the pure materials relies on the so-called mass approximation, B i.e., on neglecting the dependence of the force constants upon composition. The accuracy of such an approximation is tested and found to be very good for cationic intermixing in binary semiconductors, while it is less so for anionic substitutions. The situation is intermediate in the case of elemental semiconductors.

Physics of semiconductor devices /2nd edition/

1981-01-01

Simon M. Sze

Defects in epitaxial multilayers

1974-12-01

J. W. Matthews , A. E. Blakeslee

Computational Many-Particle Physics

2007-12-08

Holger Fehske , R. Schneider , Alexander Weiße

View PDF Chat

Semiconductor quantum dots and related systems: Electronic, optical, luminescence and related properties of low dimensional systems

2001-01-01

A. D. Yoffe

This review seeks to extend the scope of both the experimental and theoreticalwork carried out since I completed my 1993 review on the electronic, optical, andto a lesser extent, the … This review seeks to extend the scope of both the experimental and theoreticalwork carried out since I completed my 1993 review on the electronic, optical, andto a lesser extent, the transport properties of a variety of semiconductor quantumdots (QDs). In addition to the many advances that have been made on topics suchas quantum confinement effects (QCE), optical and luminescence properties,energy levels, and theoretical models that were dealt with in outline then, anumber of new themes have emerged. These include detailed studies on singleQDs such as InAs, InP, CuCl, etc, and this became possible due to thedevelopment of several microtechniques such as scanning near field opticalmicroscopy, SNOM or NSOM, as well as the use of improved growth proceduressuch as those involving MBE and the Stranski-Krastanow (SK) growth method, orby better chemical processing. By concentrating on single dots, it has provedpossible to limit the extent of the line broadening for the optical absorption andluminescence peaks due to the variation in dot sizes in the more usual types of films used. Line half widths (FWHM) in the microvolt region have now been recorded, and this has helped in the identification and resolution of excitons, biexcitons, higher excited states, and both positive and negative charged excitons, when these lie close together in energy. Quantum dots such as CdSe and CuCl which can be considered as the model systems have been the most extensively investigated, and in the case of CdSe dots, reasonable theoretical models have been developed to predict energy levels and optical properties as a function of dot size even for the difficult case of strong confinement, when R ≤ αB, the bulk exciton Bohr radius. Although problems still exist in relating predictions to all the experimental data, they have helped to identify exciton features near to and above the first main absorption peak and other optoelectronic features. A good deal of effort has now gone into the study of the III-V systems such as InP, InAs, GaAs, and GaN QDs, as well as on porous Si (PS) and Si and Ge dots. This has been largely driven by the possibility that devices such as lasers, LEDs and devices depending on single electron transport and tunnelling might be developed, an area where there is significant technological potential. For dots such as InAs etc prepared by the SK method, where there is a mismatch in lattice parameters between the InAs and the substrate such as GaAs, the dots tend to have a roughly pyramidal shaped profile, and the dot also sits on a thin InAs wetting layer. Both 2d and 3d ordered arrays of QDs can be formed using this procedure. The photoluminescence (PL) efficiency for such systems can be unexpectedly high, and there have been attempts to explain this effect as being due to the avoidance of the so-called 'phonon bottleneck' by Auger type transitions, but this is still a controversial matter. Other phenomena that are discussed include: (1) exciton- phonon coupling interactions, particularly as applied to QDs such as those formed from CuCl, CuBr, PbS, etc.; (2) coupled QDs for which dot- dot interactions need to be considered; (3) porous Si (PS), a system of considerable interest since the observation of strong PL emission features in the PL spectra by Canham in 1990, even though Si has an indirect gap, and on the practical side there has been much effort in the development of devices such as lasers, LEDs and other electroluminescence (EL) devices, and more recently for biological and medical applications, where PS, because of its porous structure, can be a host lattice for biochemical compounds in a manner similar to some zeolites. However the structure of PS is rather complex, and filaments, embryonic Si dots, as well as well formed dots, oxide interfaces of uncertain composition, and compounds containing hydrogen may all be present, and this makes it difficult to make reasonable assignments to some of the optical features present in the spectra. (4) Type II QDs that concern spatially indirect systems, and this can refer to both space and wave vector k. Instead of the electron e and hole h for an e- h pair (exciton) both residing in dot, for most of the Type II systems the h resides in the dot while the e is in the matrix in which the dots are distributed or at the interfaces. The systems considered depend on the band of sets, and include combinations such as GaAs- AlAs and CdTe- HgTe etc. (5) Hydrogenic-type donors in semiconductor QDs. (6) Excitons, biexcitons, charged excitons (both positive and negative), or trions. (7) Quantum dot- quantum well (QD-QW) combinations, also described as thin film-QD or core- shell composites, for example CdS QDs coated with a thin layer of the smaller band gap semiconductor HgS acting as a QW followed by a further CdS coating or 'clad' or 'shell'. (8) QD- conjugated organic polymer composites, a topic developed by Alivisatos, Greenham and Bawendi and their colleagues in the mid nineties, where the polymer acts as a hole conductor in an EL or LED type of device, where the wavelength of the emitted light due to e- h recombination that occurs preferably near the interface, can be varied by altering the QD radius. The possible formation of hybrid Mott-Wannier and Frenkel excitons is also briefly considered. (9) The variation of the QD dielectric constant with QD size E 2(R), has been considered by several investigators, their calculations suggest that the dielectric constant decreases substantially as R is reduced. This effect has been ignored in many contributions even though E 2 enters into the equations dealing with QSE or quantum size effects, a B, E b, and oscillator strengths (OS), and its omission will influence the calculated estimates for these quantities. (10) Finally, single electron transport and tunnelling in single and coupled QDs, and the Coulomb blockade (CB) are considered, but only in outline since this is a large problem, but it is clearly an important topic particularly in connection with the development of computing and information processing systems.

Semiconductor device fundamentals

1996-01-01

R.F. Pierret

I. SEMICONDUCTOR FUNDAMENTALS. 1. Semiconductors -- A General Introduction. General Material Properties. Crystal Structure. Crystal Growth. 2. Carrier Modeling. The Quantization Concept. Semiconductor Models. Carrier Properties. State and Carrier Distributions. … I. SEMICONDUCTOR FUNDAMENTALS. 1. Semiconductors -- A General Introduction. General Material Properties. Crystal Structure. Crystal Growth. 2. Carrier Modeling. The Quantization Concept. Semiconductor Models. Carrier Properties. State and Carrier Distributions. Equilibrium Carrier Concentrations. 3. Carrier Action. Drift. Diffusion. Recombination -- Generation. Equations of State. Supplemental Concepts. 4. Basics of Device Fabrication. Fabrication Processes. Device Fabrication Examples. R1. Part I Supplement and Review. Alternative/Supplemental Reading List. Figure Sources/Cited References. Review List of Terms. Part I Review Problem Sets and Answers. IIA. PN JUNCTION DIODES. 5. PN Junction Electrostatics. Preliminaries. Quantitative Electrostatic Relationships. 6. PN Junction Diode -- I-V Characteristics. The Ideal Diode Equation. Deviations from the Ideal. Special Considerations. 7. PN Junction Diode -- Small-Signal Admittance. Introduction. Reverse-Bias Junction Capacitance. Forward-Bias Diffusion Admittance. 8. PN Junction Diode -- Transient Response. Turn-Off Transient. Turn-On Transient. 9. Optoelectronic Diodes. Introduction. Photodiodes. Solar Cells. LEDs. IIB. BJTS AND OTHER JUNCTION DEVICES. 10. BJT Fundamentals. Terminology. Fabrication. Electrostatics. Introductory Operational Considerations. Performance Parameters. 11. BJT Static Characteristics. Ideal Transistor Analysis. Deviations from the Ideal. Modern BJT Structures. 12. BJT Dynamic Response Modeling. Equivalent Circuits. Transient (Switching) Response. 13. PNPN Devices. Silicon Controlled Rectifier (SCR). SCR Operational Theory. Practical Turn-on/Turn-off Considerations. Other PNPN Devices. 14. MS Contacts and Schottky Diodes. Ideal MS Contacts. Schottky Diode. Practical Contact Considerations. R2. Part II Supplement and Review. Alternative/Supplemental Reading List. Figure Sources/Cited References. Review List of Terms. Part II Review Problem Sets and Answers. III. FIELD EFFECT DEVICES. 15. Field Effect Introduction -- the J-FET and MESFET. General Introduction. J-FET. MESFET. 16. MOS Fundamentals. Ideal Structure Definition. Electrostatics -- Mostly Qualitative. Electrostatics -- Quantitative Formulation. Capacitance-Voltage Characteristics. 17. MOSFETs -- The Essentials. Qualitative Theory of Operation. Quantitative ID - VD Relationships. ac Response. 18. Nonideal MOS. Metal-Semiconductor Workfunction Difference. Oxide Charges. MOSFET Threshold Considerations. 19. Modern FET Structures. Small Dimension Effects. Select Structure Survey. R3. Part III Supplement and Review. Alternative/Supplemental Reading List. Figure Sources/Cited References. Review List of Terms. Part III Review Problem Sets and Answers. Appendix A. Elements of Quantum Mechanics. Appendix B. MOS Semiconductor Electrostatics -- Exact Solution. Appendix C. MOS C-V Supplement. Appendix D. MOS I-Vsupplement. Appendix E. List of Symbols. Appendix M. MATLAB Program Script.

High‐Purity Single‐Photon Emission in the Telecom O‐Band from Droplet‐Epitaxy InAs Quantum Dots Integrated into a GaAs/AlGaAs Planar Microcavity on Vicinal GaAs(111)A Platform

2025-06-25

Paweł Wyborski , Artur Tuktamyshev , Martin Arentoft Jacobsen +5 more | Advanced Quantum Technologies

Abstract Efficient single‐photon emitters operating at telecom wavelengths are pivotal for implementing long‐distance quantum communication through existing fiber‐optic networks. Here, the realization of single‐photon emission is reported in the second … Abstract Efficient single‐photon emitters operating at telecom wavelengths are pivotal for implementing long‐distance quantum communication through existing fiber‐optic networks. Here, the realization of single‐photon emission is reported in the second telecom window from droplet‐epitaxy InAs quantum dots (QDs) integrated into a GaAs‐based photonic structure. By employing an InAlAs metamorphic buffer layer to engineer strain, telecom‐wavelength emission is achieved over a broad range of 1170–1360 nm, while maintaining compatibility with mature GaAs device platforms. Embedded in a planar GaAs/AlGaAs distributed Bragg reflector microcavity, these QDs exhibit high‐purity single‐photon emission, as indicated by a second‐order correlation function = under continuous‐wave excitation and = under pulsed above‐band excitation. Time‐resolved photoluminescence measurements yield a short average lifetime of about 0.98 ns, and the cavity design improves the extraction efficiency up to 5.8‐fold, with a value of approximately 3.9 to the first lens. These results highlight the potential of droplet‐epitaxy InAs QDs for scalable, fiber‐compatible quantum photonic technologies and pave the way for practical long‐distance quantum communication.

Excitons in fractionally filled moiré superlattices

2025-06-23

NULL AUTHOR_ID | Physical review. B./Physical review. B

MOCVD-grown InAs/InP quantum dot lasers with low threshold current

2025-06-20

Zhao Yan , Shangfeng Liu , Bogdan‐Petrin Ratiu +7 more | Optics Express

Design and optimization of In(Ga)As quantum dot single photon source based on air gap structure

2025-06-19

Xiaoyang Zhao , Yidi Bao , Xiaoling Chen +3 more | Materials Science and Engineering B

Impact of structural defects on the creation of the electronic localized states in quasi-periodic GaAs/GaAlAs multi-quantum wells

2025-06-18

Fatima Zahra Elamri , Abdelkader Baidri , Farid Falyouni +1 more | Applied Physics A

Energy bandgap of ZnSe bulk crystal between 300 K and 1000 K

2025-06-18

Ching‐Hua Su | Materials Letters

Polarization purity and cross-channel intensity correlations

2025-06-16

Daniel Kestner , Alexander B. Kostinski | Journal of the Optical Society of America A

Negative photoconductivity induced by carrier trapping in hyperdoped silicon

2025-06-15

Zhiqiang Cao , Xin-Hua Deng , Huihuang Yang +7 more | Materials Science in Semiconductor Processing

Advanced characterization and parameter extraction of electrically injected InGaAs/GaAs nano-ridge lasers monolithically integrated on silicon

2025-06-12

Andualem Yimam , Davide Colucci , Charles Caër +7 more | Optics Express

Exciton Insulators in Two-dimensional Systems

2025-06-12

Huaiyuan Yang , Xi Dai , Xin-Zheng Li | Chinese Physics B

Abstract Electron-hole interaction plays a crucial role in determining the optoelectronic properties of materials, and in low-dimensional systems this is especially true due to the decrease of screening. In this … Abstract Electron-hole interaction plays a crucial role in determining the optoelectronic properties of materials, and in low-dimensional systems this is especially true due to the decrease of screening. In this review, we focus on one unique quantum phase induced by the electron-hole interaction in two-dimensional systems, known as “exciton insulators” (EIs). Although this phase of matter has been studied for more than half a century, suitable platforms for its stable realization remain scarce. We provide an overview of the strategies to realize EIs in accessible materials and structures, along with a discussion on some unique properties of EI stemming from the band structure of these materials. Additionally, signatures in experiments to distinguish EIs are also discussed.

Deterministic Fabrication of GaAs‐Quantum‐Dot Micropillar Single‐Photon Sources

2025-06-11

Abdulmalik A. Madigawa , Martin Arentoft Jacobsen , Claudia Piccinini +6 more | Advanced Quantum Technologies

Abstract This study investigates the performance of droplet‐etched GaAs quantum dots (QDs) integrated into micropillar structures using a deterministic fabrication technique. A unity QD positioning yield across 74 devices and … Abstract This study investigates the performance of droplet‐etched GaAs quantum dots (QDs) integrated into micropillar structures using a deterministic fabrication technique. A unity QD positioning yield across 74 devices and consistent device performanceare demonstrated. Under p‐shell excitation, the QD decay dynamics within the micropillars exhibit biexponential behavior, accompanied by intensity fluctuations limiting the source efficiency to < 4.5%. Charge stabilization via low‐power above‐band LED excitation effectively reduces these fluctuations, doubling the source efficiency to 9%. Moreover, suppression of radiation modes is introduced by implementing cylindrical rings theoretically predicted to boost the collection efficiency by a factor of 4. Experimentally, only a modest improvement is obtained, underscoring the influence of even minor fabrication imperfections for this advanced design. These findings demonstrate the reliability of the deterministic fabrication approach in producing high‐yield, uniform devices, while offering detailed insights into the influence of charge noise and complex relaxation dynamics on the performance.

Injection and All‐Optical Coherent Control of Ultrafast Photocurrent in 2D SnSe2 Film Excited by Dual‐Color Laser Fields

2025-06-07

Xiangyu La , Yuhang He , Yuxuan Chen +4 more | Laser & Photonics Review

Abstract The 2D material tin diselenide (SnSe 2 ) exhibits remarkable potential within the optoelectronics domain, attributed to its distinctive electronic structure and optical characteristics. Under dual‐color laser field excitation … Abstract The 2D material tin diselenide (SnSe 2 ) exhibits remarkable potential within the optoelectronics domain, attributed to its distinctive electronic structure and optical characteristics. Under dual‐color laser field excitation at 800 and 400 nm, the injection and coherent control of ultrafast photocurrent in SnSe 2 are complex owning to its direct and indirect bandgap energies being below the fundamental photon energy. The photocurrent injection in SnSe 2 is studied via measuring its emitted terahertz wave. There are two quantum interference channels: one between single‐ and two‐photon absorptions, and the other between stimulated electronic Raman scattering and single‐photon absorption. Both induce asymmetric carrier distribution in momentum space, leading to coherent photocurrent injection. Moreover, under the collinearly polarized dual‐color laser field excitation, the amplitude and polarity of THz radiation (photocurrent) can be coherently controlled by altering the relative phase of the laser fields. When the fields are co‐circularly polarized, the polarization direction of emitted THz radiation can be coherently controlled by relative phase, and its rotation direction depends on the helicity of the circularly polarized fields. This work improves the understanding of electron transitions and ultrafast photocurrent injection in narrow‐bandgap SnSe 2 and offers an all‐optical method for the coherent control of ultrafast photocurrent.

Fast recovery dynamics of GaSbBi-based SESAMs for high-fluence operation

2025-06-02

Maximilian C. Schuchter , Joonas Hilska , M. Peil +4 more | Applied Physics Letters

Modelocked lasers operating in the 2–3 μm wavelength region are interesting for various spectroscopic applications. To this end, GaSb-based semiconductor saturable absorber mirrors (SESAMs) are developing fast as a practical … Modelocked lasers operating in the 2–3 μm wavelength region are interesting for various spectroscopic applications. To this end, GaSb-based semiconductor saturable absorber mirrors (SESAMs) are developing fast as a practical technology for passive modelocking. Yet, such SESAMs suffer from either too high two-photon absorption or slow absorption recovery dynamics. This study introduces GaSbBi quantum wells (QWs) as a platform to ensure a larger material selection for engineering GaSb-based SESAMs with decreased two-photon absorption and ultrafast absorption recovery time. Three GaSbBi QW SESAM designs were fabricated to compare their performance against conventional GaInSb QW SESAMs. The first structure makes use of typical GaSb barriers and exhibits comparable characteristics to the conventional design, including a saturation fluence of 1.09 μJ cm−2, a modulation depth of 1.41%, and a fast interband recovery time of 6.03 ps. The second design incorporated AlAs0.08Sb0.92 barriers, achieving a reduced two-photon absorption, though at the cost of higher nonsaturable losses due to unintended Bi droplet formation during the growth of the AlAs0.08Sb0.92/GaSbBi QW heterostructure. Importantly, it maintained a fast interband recovery time (30 ps), overcoming the slow recovery dynamics exhibited by standard GaInSb QW SESAMs with AlAs0.08Sb0.92 barriers. The third design explored GaSbBi QWs with higher Bi content targeted for longer wavelength operation at 2.3 μm, which exhibited fast recovery times and good nonlinear reflectivity characteristics. However, the higher Bi content resulted in elevated nonsaturable losses. These results highlight the potential of GaSbBi QWs for short-wave infrared (SWIR) SESAMs, opening the path for further epitaxial optimization to enhance their performance.

Having a good vibe: Strong coupling to the electronic system creates incoherent and coherent phonons in 1L-TMDCs

2025-06-02

Tim Völzer , Marvin Krupp , Julian Schröer +3 more | 2D Materials

Abstract The electronic dynamics in monolayer transition metal dichalcogenides (1L-TMDCs) following optical excitation crucially determine all their optoelectronic applications. The basic processes can be divided into energy redistribution leasing to … Abstract The electronic dynamics in monolayer transition metal dichalcogenides (1L-TMDCs) following optical excitation crucially determine all their optoelectronic applications. The basic processes can be divided into energy redistribution leasing to a thermal equilibrium of the electronic and the phononic system, and the recombination of the excited species. Furthermore, the displacive excitation of coherent phonons assigned to the A' 1 Raman mode has been demonstrated employing sufficiently short pump pulses. In this study, we shed light on the ultrafast dynamics of three different 1L-TMDCs using transient absorption (TA) spectroscopy. We reveal a cascade-like cooling of the excited electronic states, owing to their differing coupling strengths to high- versus low-energy phonons. In addition, the coherently excited lattice vibrations imprint a strong oscillatory contribution onto the signal. We extract a dominating, spectrally broad signature of the A' 1 mode, whose shape challenges existing models. On top of that, we identify a second frequency band matching the E' Raman peak in 1L-WS 2 . Finally, measurements at high pump fluences demonstrate a phonon bottleneck for the cooling cascade. Simultaneously, the dominant A' 1 mode softens, providing a new degree of tunability for these coherent lattice vibrations. Overall, our findings demonstrate the strong couplings between the electronic and phononic (sub)systems in 1L-TMDCs.

Local droplet etching with In, Al and InAl in In0.52Al0.48As layers for generation of quantum dots emitting in the optical C-band

2025-06-01

D. Deutsch , Viktoryia Zolatanosha , D. Reuter | Journal of Crystal Growth

Binding energy of excitons in quantum wells with embedded series of thin tunnel-transparent barriers

2025-06-01

M. P. Telenkov , P. F. Kartsev , P. S. Klemmer +2 more | Indian Journal of Physics

The impact of the external magnetic field on <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"><mml:msubsup><mml:mi>D</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow><mml:mo>+</mml:mo></mml:msubsup></mml:math> ion ground state properties in a Gaussian GaAs quantum dot

2025-06-01

Siddartha Gone , Divya Rani Gunty , Madhusudan Gorre +2 more | Journal of Magnetism and Magnetic Materials

Investigation of light trapping from P-N Interleaved Structure-based absorber layer for the efficiency enhancement of In0.4Ga0.6N homo junction solar cell

2025-06-01

Swati S Soley , Shrikant Verma , Narendra Khatri | Micro and Nanostructures

Modelling of strain effects in core/shell QDs with tight binding theory and k.p effective mass approximation

2025-06-01

Derya Malkoç , B Danacı , Hilmi Ünlü | Journal of Physics Conference Series

Abstract Reliable predictions of the potential of nanoscale semiconductor heterostructures for nanodevice fabrication require accurate theoretical models and precise numerical calculations to assess how strain affects their electronic, optical and … Abstract Reliable predictions of the potential of nanoscale semiconductor heterostructures for nanodevice fabrication require accurate theoretical models and precise numerical calculations to assess how strain affects their electronic, optical and structural properties. The second nearest neighbour (2NN) sp3s* tight binding model and the four-band k.p effective mass approximation are employed to analyze impact of strain on the optical, electronic and structural properties in nanoscale spherical CdSe and ZnSe-based core/shell quantum dots (QDs) in this study. According to our analysis, when the shell diameter increases linearly, keeping the core diameter constant, core bandgaps increase parabolically in ZnSe/ZnS and CdSe/Cd(Zn)S QDs but decrease parabolically in ZnSe/CdS QDs. Furthermore, with a constant shell diameter, an increase in core diameter results in a parabolic decrease of core bandgaps in all four QD types. The proposed model can serve as an effective design tool for simulating nanoscale core/shell heterostructures in quantum dot-based nanodevices.

Transparency Current and Gain Spectrum of InGaAs/GaAs Quantum Well-Dots

2025-05-30

G. O. Kornyshov , A. S. Payusov , A. A. Kharchenko +6 more | Journal of Applied Spectroscopy

The role of cladding layer thickness in InAsPSb/InGaAs MQW IR LED performance

2025-05-30

S. Bahareh Seyedein Ardebili , Behnam Zeinalvand Farzin , Jong Su Kim | Journal of Computational Electronics

Cryogenic sub-THz ultrathin-body InGaAs MOSFET: physical modeling and DC/RF analysis

2025-05-30

Sri Sai , Navaneeth Madathil , D. Kannadassan | Journal of Computational Electronics

Effect of relaxation temperature on the growth quality of zinc-blende and wurtzite GaAs films

2025-05-28

Wenwen Tian , Tinghong Gao , Qian Chen +1 more | Physica Scripta

Abstract Ⅲ–Ⅴ type semiconductor gallium arsenide (GaAs) has been widely used in medical devices, circuit components, chip manufacturing, and other fields. GaAs will have high commercial value in the future … Abstract Ⅲ–Ⅴ type semiconductor gallium arsenide (GaAs) has been widely used in medical devices, circuit components, chip manufacturing, and other fields. GaAs will have high commercial value in the future development of new energy. In addition to the widely used zinc-blende-structured GaAs, wurtzite-structured GaAs has certain development prospects. This study uses the molecular dynamics simulation method to study the effect of relaxation temperature on the crystallization quality of polycrystalline GaAs. A solid–liquid GaAs model obtained after deposition was established to simulate growth, and the growth phenomenon of zinc-blende- and wurtzite-structured GaAs crystals at three relaxation temperatures of 1600 K, 1700 K, and 1800 K was simulated. The results show that increasing the relaxation temperature within a certain range eliminates the As8 structure that appears during the growth process, which increases the crystallization rate of GaAs crystals. Stacking fault energy was used to analyze surface defect phenomena. The calculating results indicate that zinc-blende stacking faults occur in crystals with very high or very low unstable stacking fault energy, while wurtzite stacking faults usually occur in crystals with low unstable stacking fault energy. In the [111] [112] [0001] crystal phases where stacking faults occur, the unstable stacking fault energy decreases as temperature increases and the occurrence probability of stacking faults decreases.

Magneto-Exciton Energy in Cylindrical Indium Arsenide Quantum Dots Affected by External Parameters

2025-05-27

Marwan Zuhair Elias | Scientific Journal of King Faisal University Basic and Applied Sciences

The effects of temperature, pressure, and an applied magnetic field on the energies of a cylindrical layer of indium arsenide (InAs) quantum dots, with and without Coulomb interaction, are investigated. … The effects of temperature, pressure, and an applied magnetic field on the energies of a cylindrical layer of indium arsenide (InAs) quantum dots, with and without Coulomb interaction, are investigated. Exciton energy depends significantly on these parameters. The results show that the ground-state and excited-state energies increase with rising temperature and applied magnetic field (blue shift), but that both energy states decrease with increasing pressure (red shift). As the temperature increases for higher states, the sensitivity of magneto-exciton energy also increases. The outcomes obtained for layered and ring-shaped systems exhibit a universal quality, making them particularly interesting. KEYWORDS Exciton, magnetic field, nanostructures, potential, pressure, temperature

Strain relief and threading dislocation reduction in GaSb/AlSb/GaSb heterostructures grown on Si(001) substrate

2025-05-27

Karl Graser , Audrey Gilbert , Jean‐Baptiste Rodriguez +2 more

The monolithic integration of III-Sb materials on Si substrates enables the development of novel functionalities and promising device applications. However, due to the large lattice mismatch to Si, direct heteroepitaxy … The monolithic integration of III-Sb materials on Si substrates enables the development of novel functionalities and promising device applications. However, due to the large lattice mismatch to Si, direct heteroepitaxy of III-Sb results in a very large and disadvantageous dislocation density. Here, we report on the effect of strained AlSb interlayers in GaSb as dislocation filters for the epitaxy on Si(001) substrates. The epitaxial stress introduced by the lattice mismatched AlSb layer leads to threading dislocation bending at the interfaces as a strain relieving mechanism, thereby facilitating the reaction and annihilation of dislocations during their lateral glide process. Using comprehensive electron channeling contrast imaging and scanning transmission electron microscopy, we measure the dislocation density at the surface and after filter and cap layers of different thicknesses and analyze the effect of plastic strain relaxation on dislocation reduction. The reduction mechanism is discussed in the context of misfit dislocation networks forming at the respective compressively and tensile strained interfaces. With the new findings, an effective double filter layer structure with adopted layer thicknesses could be realized, which has resulted in a very low threading dislocation density of 1.7×107cm−2.