Magnetoexcitons in Type-II Self-Assembled Quantum Dots and Quantum-Dot Superlattices

2006 ◽  
Vol 518 ◽  
pp. 51-56
Author(s):  
Dj. Veljković ◽  
M. Tadić ◽  
F.M. Peeters
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Angular Momentum ◽  
Quantum Dot ◽  
Oscillator Strength ◽  
Band Alignment ◽  
Type Ii ◽  
Angular Momenta ◽  
Self Assembled ◽  
The Magnetic Field

Exciton states in type-II InP/InGaP and GaSb/GaAs self-assembled quantum dots and quantum-dot superlattices subject to a normal magnetic field are calculated. Strain is explicitly taken into account in single particle models of the electronic structure, while an exact diagonalization approach is adopted to compute the exciton states. Strain reverts type II band alignment in InP quantum dots to type I, therefore no transitions between the lowest energy states of different angular momenta are observed. On the other hand, strain increases the barrier for the electron in the conduction band of GaSb/GaAs quantum dots, therefore the exciton, being composed of electron and hole states of various angular momenta, may have a finite angular momentum in the ground state. Consequently, the oscillator strength in the InP single quantum dot and quantum-dot superlattice increases with the magnetic field, while the angular momentum transitions between the bright and the dark exciton states in the GaSb system bring about decay of the oscillator strength when the magnetic field exceeds a certain value.

scholarly journals Effect of magnetic field and impurities in InAs/GaAs and GaN/AlN self-assembled quantum dots

2019 ◽  
Vol 65 (3) ◽  
pp. 231
Author(s):  
G. Linares García ◽  
And L. Meza-Montes
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Probability Density ◽  
Electronic States ◽  
Zeeman Splitting ◽  
Growth Direction ◽  
Two Systems ◽  
Piezoelectric Effects ◽  
Self Assembled ◽  
The Magnetic Field

A theoeritical study on the effect of a magnetic field or impurities on the carries states of self-assembled quantum dots is presented. The magnetic field is applied along the growth direction of the dots, and for comparison two systems are considered, InAs embeded in GaAs, and GaN in AlN. The electronic states and energy are calculated in the framework of the k.p theory in 8 bands including the strain and piezoelectric effects. Zeeman splitting and anticrossings are observed in InAs/GaAs, while the field introduces small changes in the nitrides. It is also included a study about hidrogen-like impurities, which may be negative or positive. It is noted that depending on the type of impurity, the confinement energy of carriers is changed, and the distribution of the probability density of the carriers is affected  too.

Coexistence of type-I and type-II band alignment in Ga(Sb, P)/GaP heterostructures with pseudomorphic self-assembled quantum dots

JETP Letters ◽  
2014 ◽  
Vol 99 (2) ◽  
pp. 76-81 ◽  
Author(s):  
D. S. Abramkin ◽  
V. T. Shamirzaev ◽  
M. A. Putyato ◽  
A. K. Gutakovskii ◽  
T. S. Shamirzaev
Keyword(s):  
Quantum Dots ◽  
Band Alignment ◽  
Type I ◽  
Type Ii ◽  
Self Assembled

Energy Spectra of the Low-Lying State in N-Layer Quantum Dots

2013 ◽  
Vol 483 ◽  
pp. 170-173
Author(s):  
An Mei Wang
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Angular Momentum ◽  
External Magnetic Field ◽  
Quantum Dot ◽  
Applied Magnetic Field ◽  
Ground State ◽  
Weak Coupling ◽  
State Energy ◽  
Energy Spectra

A method is proposed to exactly diagonalize the Hamiltonian of a N-layer quantum dot containing a single electron in each dot in arbitrary magnetic fields. the energy spectra of the dot are calculated as a function of the applied magnetic field. We find disco-ntinuous ground-state energy transitions induced by an external magnetic field in the case of strong coupling. However, in the case of weak coupling, such a transition does not occur and the angular momentum remains zero.

Observation of Band Alignment Transition from Type-I to Type-II in AlInAs/AlGaAs Self-assembled Quantum Dots

2003 ◽  
Vol 72 (12) ◽  
pp. 3271-3275 ◽  
Author(s):  
Keisuke Ohdaira ◽  
Hiroshi Murata ◽  
Shinji Koh ◽  
Motoyoshi Baba ◽  
Hidefumi Akiyama ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Band Alignment ◽  
Type I ◽  
Type Ii ◽  
Self Assembled

Magneto-photoluminescence Studies of AlInAs/AlGaAs Self-assembled Quantum Dots with Type-II Band Alignment

2004 ◽  
Vol 73 (2) ◽  
pp. 480-484
Author(s):  
Keisuke Ohdaira ◽  
Kazuo Ono ◽  
Kazuhito Uchida ◽  
Shinji Koh ◽  
Noboru Miura ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Band Alignment ◽  
Type Ii ◽  
Self Assembled ◽  
Photoluminescence Studies

DIRECT BANDGAP QUANTUM DOTS EMBEDDED IN A TYPE-II GaAs/AlAs DOUBLE QUANTUM WELL STRUCTURE

2007 ◽  
Vol 21 (08n09) ◽  
pp. 1654-1658 ◽  
Author(s):  
BARBARA CHWALISZ-PIȨTKA ◽  
ANDRZEJ WYSMOŁEK ◽  
ROMAN STȨPNIEWSKI ◽  
MAREK POTEMSKI ◽  
SYLVAIN RAYMOND ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Excited States ◽  
Surface Density ◽  
Three Dimensional ◽  
Spin Splitting ◽  
Double Quantum ◽  
Type Ii ◽  
Double Quantum Well ◽  
The Magnetic Field

Quantum dots with strong three dimensional confinement and low surface density have been identified in a structure which was nominally grown as a type-II GaAs/AlAs bilayer surrounded by GaAlAs barriers. Micro-luminescence experiments in magnetic fields performed on these dots display excitonic spin-splitting and orbital Zeeman effects for the excited states. The modification by the magnetic field of the diffusion and/or trapping of photoexcited carriers into the dots is also observed.

Optical signatures of type I–type II band alignment transition in Cd(Se,Te)/ZnTe self-assembled quantum dots

2020 ◽  
Vol 117 (11) ◽  
pp. 113101
Author(s):  
Piotr Baranowski ◽  
Małgorzata Szymura ◽  
Grzegorz Karczewski ◽  
Marta Aleszkiewicz ◽  
Aleksander Rodek ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Band Alignment ◽  
Type I ◽  
Type Ii ◽  
Self Assembled

SPACE-CHARGE SPECTROSCOPY OF ELECTRONIC STATES IN Ge/Si QUANTUM DOTS WITH TYPE-II BAND ALIGNMENT

2007 ◽  
Vol 06 (05) ◽  
pp. 353-356
Author(s):  
A. I. YAKIMOV ◽  
A. V. DVURECHENSKII ◽  
A. I. NIKIFOROV ◽  
A. A. BLOSHKIN
Keyword(s):  
Quantum Dots ◽  
Electronic Structure ◽  
Binding Energy ◽  
Space Charge ◽  
Tensile Strain ◽  
Electronic States ◽  
Band Alignment ◽  
Type Ii ◽  
Electron Confinement ◽  
Si Quantum Dots

Space-charge spectroscopy was employed to study electronic structure in a stack of four layers of Ge quantum dots coherently embedded in an n-type Si (001) matrix. Evidence for an electron confinement in the vicinity of Ge dots was found. From the frequency-dependent measurements the electron binding energy was determined to be ~50 meV, which is consistent with the results of numerical analysis. The data are explained by a modification of the conduction band alignment induced by inhomogeneous tensile strain in Si around the buried Ge dots.

scholarly journals Analyzing the propagation of EUV waves and their connection with type II radio bursts by combining numerical simulations and multi-instrument observations

2020 ◽  
Vol 644 ◽  
pp. A90
Author(s):  
A. Koukras ◽  
C. Marqué ◽  
C. Downs ◽  
L. Dolla
Keyword(s):  
Magnetic Field ◽  
Wave Front ◽  
Ray Tracing ◽  
Radio Burst ◽  
Radio Bursts ◽  
Type Ii ◽  
Fast Mode ◽  
Type Ii Radio Bursts ◽  
The Magnetic Field ◽  
Burst Emission

Context. EUV (EIT) waves are wavelike disturbances of enhanced extreme ultraviolet (EUV) emission that propagate away from an eruptive active region across the solar disk. Recent years have seen much debate over their nature, with three main interpretations: the fast-mode magneto-hydrodynamic (MHD) wave, the apparent wave (reconfiguration of the magnetic field), and the hybrid wave (combination of the previous two). Aims. By studying the kinematics of EUV waves and their connection with type II radio bursts, we aim to examine the capability of the fast-mode interpretation to explain the observations, and to constrain the source locations of the type II radio burst emission. Methods. We propagate a fast-mode MHD wave numerically using a ray-tracing method and the WKB (Wentzel-Kramers-Brillouin) approximation. The wave is propagated in a static corona output by a global 3D MHD Coronal Model, which provides density, temperature, and Alfvén speed in the undisturbed coronal medium (before the eruption). We then compare the propagation of the computed wave front with the observed wave in EUV images (PROBA2/SWAP, SDO/AIA). Lastly, we use the frequency drift of the type II radio bursts to track the propagating shock wave, compare it with the simulated wave front at the same instant, and identify the wave vectors that best match the plasma density deduced from the radio emission. We apply this methodology for two EUV waves observed during SOL2017-04-03T14:20:00 and SOL2017-09-12T07:25:00. Results. The simulated wave front displays a good qualitative match with the observations for both events. Type II radio burst emission sources are tracked on the wave front all along its propagation. The wave vectors at the ray-path points that are characterized as sources of the type II radio burst emission are quasi-perpendicular to the magnetic field. Conclusions. We show that a simple ray-tracing model of the EUV wave is able to reproduce the observations and to provide insight into the physics of such waves. We provide supporting evidence that they are likely fast-mode MHD waves. We also narrow down the source region of the radio burst emission and show that different parts of the wave front are responsible for the type II radio burst emission at different times of the eruptive event.

scholarly journals Investigation of Light Absorption in a ZnS Quantum Dot

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
Hojjatollah K. Salehani ◽  
Maedeh Zakeri
Keyword(s):  
Magnetic Field ◽  
Optical Absorption ◽  
Quantum Dot ◽  
Excited States ◽  
Light Absorption ◽  
Blue Shift ◽  
Optical Absorption Coefficient ◽  
Parabolic Confinement ◽  
Parabolic Confinement Potential ◽  
The Magnetic Field

The light absorption of a ZnS quantum dot with a parabolic confinement potential is studied in this paper in the presence of magnetic field perpendicular to dot plane. The Schrodinger equation of a single electron is solved numerically, and energy spectra and wave functions are obtained. Then, the optical absorption coefficients in transition from ground state to different excited states are calculated. The effects the magnetic field and quantum dot width on the optical absorption are investigated. It is found that the optical absorption coefficient has a blue shift by increasing of magnetic field or confinement strength of quantum dot.

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