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

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.

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Zeeman splitting, Zeeman transitions and optical absorption of an electron confined in spherical quantum dots under the magnetic field

The Philosophical Magazine A Journal of Theoretical Experimental and Applied Physics ◽

10.1080/14786435.2020.1821112 ◽

2020 ◽

pp. 1-12

Author(s):

E. B. Al ◽

E. Kasapoglu ◽

H. Sari ◽

I. Sökmen

Keyword(s):

Magnetic Field ◽

Quantum Dots ◽

Optical Absorption ◽

Zeeman Splitting ◽

The Magnetic Field

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.518.51 ◽

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.

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Magnetooptical Studies of Acceptors Confined in GaAs/AIGaAs Quantum Wells

MRS Proceedings ◽

10.1557/proc-325-73 ◽

1993 ◽

Vol 325 ◽

Author(s):

P.O. Holtz ◽

Q.X. Zhao ◽

B. Monemar ◽

A. Pasquarello ◽

M. Sundaram ◽

...

Keyword(s):

Magnetic Field ◽

Quantum Wells ◽

Ground State ◽

Energy Levels ◽

Zeeman Splitting ◽

Growth Direction ◽

Bulk Gaas ◽

Theoretical Predictions ◽

Resonant Raman ◽

The Magnetic Field

AbstractMagnetooptical studies have been performed on the shallow Be acceptor confined in the central region of narrow GaAs/AlGaAs quantum wells (QWs) with the magnetic field along the growth direction. The magnetic field dependence of the acceptor transition between the 1S(Г6) hh-like ground state and the excited hh-like 2S(Г6) state has been investigated by means of two independent techniques: Two-hole transitions of the acceptor bound exciton (BE) and resonant Raman scattering. The 1S(Г6) – 2S(Г6) transition energy as a function of the magnetic field has been measured for central acceptors in QWs of widths in the range 50 – 150 Å. The energy levels for the 1S ground states and 2S excited states of the confined acceptor with a magnetic field as a perturbation have also been calculated. These calculations predict a larger splitting between the mj=+3/2 and mj=−3/2 components of the acceptor 1S(Г6) ground state in comparison with the corresponding splitting of the excited 2S(Г6) state. The experimental results are in good agreement with the theoretical predictions derived without any fitting parameters. Furthermore, the Zeeman splitting of the acceptor BE emission has been measured and it is concluded that the J = 5/2 BE state is lowest in energy, similar to shallow acceptor BEs in bulk GaAs.

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The magnetic field in the dense photodissociation region of DR 21

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3898 ◽

2020 ◽

Author(s):

Atanu Koley ◽

Nirupam Roy ◽

Karl M Menten ◽

Arshia M Jacob ◽

Thushara G S Pillai ◽

...

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Zeeman Effect ◽

Zeeman Splitting ◽

Weak Field ◽

Field Energy ◽

Evolutionary Stage ◽

Maser Emission ◽

The Magnetic Field ◽

Photodissociation Region

Abstract Measuring interstellar magnetic fields is extremely important for understanding their role in different evolutionary stages of interstellar clouds and of star formation. However, detecting the weak field is observationally challenging. We present measurements of the Zeeman effect in the 1665 and 1667 MHz (18 cm) lines of the hydroxyl radical (OH) lines toward the dense photodissociation region (PDR) associated with the compact H ii region DR 21 (Main). From the OH 18 cm absorption, observed with the Karl G. Jansky Very Large Array, we find that the line of sight magnetic field in this region is ∼0.13 mG. The same transitions in maser emission toward the neighbouring DR 21(OH) and W 75S-FR1 regions also exhibit the Zeeman splitting. Along with the OH data, we use [C ii] 158 μm line and hydrogen radio recombination line data to constrain the physical conditions and the kinematics of the region. We find the OH column density to be ∼3.6 × 1016(Tex/25 K) cm−2, and that the 1665 and 1667 MHz absorption lines are originating from the gas where OH and C+ are co-existing in the PDR. Under reasonable assumptions, we find the measured magnetic field strength for the PDR to be lower than the value expected from the commonly discussed density–magnetic field relation while the field strength values estimated from the maser emission are roughly consistent with the same. Finally, we compare the magnetic field energy density with the overall energetics of DR 21’s PDR and find that, in its current evolutionary stage, the magnetic field is not dynamically important.

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The Magnetic Field Near the Local Bubble

International Astronomical Union Colloquium ◽

10.1017/s0252921100071037 ◽

1997 ◽

Vol 166 ◽

pp. 227-238

Author(s):

Carl Heiles

Keyword(s):

Magnetic Field ◽

Large Scale ◽

Zeeman Splitting ◽

Relativistic Electrons ◽

Local Bubble ◽

Scale Field ◽

Large Scale Field ◽

Field Lines ◽

Hi Shells ◽

The Magnetic Field

AbstractThere are almost no direct observational indicators of the magnetic field inside the local bubble. Just outside the bubble, the best tracers are stellar polarization and HI Zeeman splitting. These show that the local field does not follow the large-scale Galactic field. Here we discuss whether the deformation of the large-scale field by the local HI shells is consistent with the observations. We concentrate on the Loop 1 region, and find that the field lines are well-explained by this idea; in addition, the bright radio filaments of Radio Loop 1 delineate particular field lines that are “lit up” by an excess of relativistic electrons.

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Microstructures and Growth Characteristics of Self-Assembled InAs/GaAs Quantum Dots Investigated by Transmission Electron Microscopy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.26-28.1207 ◽

2007 ◽

Vol 26-28 ◽

pp. 1207-1210

Author(s):

Hyung Seok Kim ◽

Ju Hyung Suh ◽

Chan Gyung Park ◽

Sang Jun Lee ◽

Sam Kyu Noh ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Quantum Dots ◽

Chemical Potential ◽

Early Stage ◽

Compressive Strain ◽

Potential Gradient ◽

Growth Direction ◽

Transmission Electron ◽

Self Assembled

The microstructure and strain characteristics of self-assembled InAs/GaAs quantum dots (QDs) were studied by using transmission electron microscopy. Compressive strain was induced to uncapped QDs from GaAs substrate and the misfit strain largely increased after the deposition of GaAs cap layer. Tensile strain outside QD was extended along the vertical growth direction; up to 15 nm above the wetting layer. Vertically nonaligned and aligned stacked QDs were grown by adjusting the thickness of GaAs spacer layers. The QDs with a lens-shaped morphology were formed in the early stage of growth, and their apex was flattened by the out-diffusion of In atoms upon GaAs capping. However, aligned QDs maintained their lens-shaped structure with round apex after capping. It is believed that their apex did not flatten because the chemical potential gradient of In was relatively low due to the adjacent InAs QD layers.

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Magnetic Fields in OH Maser Clouds

Symposium - International Astronomical Union ◽

10.1017/s0074180900026565 ◽

1974 ◽

Vol 60 ◽

pp. 275-292 ◽

Cited By ~ 1

Author(s):

R. D. Davies

Keyword(s):

Magnetic Field ◽

Angular Momentum ◽

Magnetic Fields ◽

Magnetic Flux ◽

Field Data ◽

Zeeman Splitting ◽

Galactic Rotation ◽

Magnetic Field Data ◽

The Magnetic Field ◽

Maser Sources

Observations of Class I OH maser sources show a range of features which are predicted on the basis of Zeeman splitting in a source magnetic field. Magnetic field strengths of 2 to 7 mG are derived for eight OH maser sources. The fields in all the clouds are directed in the sense of galactic rotation. A model of W3 OH is proposed which incorporates the magnetic field data. It is shown that no large amount of magnetic flux or angular momentum has been lost since the condensation from the interstellar medium began.

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