scholarly journals Theoretical Study of Excitonic Complexes in GaAs/AlGaAs Quantum Dots Grown by Filling of Nanoholes

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Mohamed Omri ◽  
Amor Sayari ◽  
Larbi Sfaxi
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Fine Structure ◽  
Theoretical Study ◽  
Three Dimensional ◽  
Correlation Effect ◽  
Wave Functions ◽  
Transition Energies ◽  
New Family ◽  
Effective Mass Schrödinger Equation

In this work, a theoretical study of the electronic and the optical properties of a new family of strain-free GaAs/AlGaAs quantum dots (QDs) obtained by AlGaAs nanohole filling is presented. The considered model consists of solving the three-dimensional effective-mass Schrödinger equation, thus providing a complete description of the neutral and charged complex excitons’ fine structure. The QD size effect on carrier confinement energies, wave functions, and s-p splitting is studied. The direct Coulomb interaction impact on the calculated s and p states’ transition energies is investigated. The behaviour of the binding energy of neutral and charged excitons (X− and X+) and biexciton XX versus QD height is studied. The addition of the correlation effect allows to explain the nature of biexcitons often observed experimentally.

Interband Optical Transition Energies in Type-II PbSe/PbS Core/Shell Quantum Dots

2017 ◽  
Vol 6 (1) ◽  
pp. 80-86
Author(s):  
S. N. Saravanamoorthy ◽  
A. John Peter
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Shell Thickness ◽  
Optical Transition ◽  
Hole Pair ◽  
Core Shell ◽  
Type Ii ◽  
Electron Hole ◽  
Transition Energies ◽  
Electron Hole Pair

Electronic and optical properties of Type-II lead based core/shell semiconducting quantum dots are reported. Binding energies of electron–hole pair, optical transition energies and the absorption coefficients are investigated taking into account the geometrical confinement in PbSe/PbS core/shell quantum dot nanostructure. The energies are obtained with the increase of shell thickness for various inner core radii. The probability densities of electron and hole wave functions of radial coordinate of the core PbSe and PbS shell quantum dots are presented. The optical transition energy with the spatial confinement is brought out. The electronic properties are obtained using variational approach whereas the compact density matrix method is employed for the nonlinear optical properties. The results show that (i) a decrease in binding energy is obtained when the shell thickness increases due to more separation of electron–hole pair and (ii) the energy band gap decreases with the increase in the shell thickness resulting in the reduction of the higher energy interband transitions.

Modeling of elastic, piezoelectric and optical properties of vertically correlated GaN/AlN quantum dots

2004 ◽  
Vol 831 ◽  
Author(s):  
Sławomir P. Łepkowski ◽  
Grzegorz Jurczak ◽  
Paweł Dłużewski ◽  
Tadeusz Suski
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Quantum Dot ◽  
Quantum Wells ◽  
Electrostatic Potential ◽  
Barrier Width ◽  
Base Diameter ◽  
Transition Energies ◽  
Band Transition ◽  
Hexagonal Pyramid

ABSTRACTWe theoretically investigate elastic, piezoelectric and optical properties of wurtzite GaN/AlN quantum dots, having hexagonal pyramid-shape, stacked in a multilayer. We show that the strain existing in quantum dots and barriers depends significantly on the distance between the dots i.e. on the width of AlN barriers. For typical QDs, having the base diameter of 19.5nm, the drop of the electrostatic potential in the quantum dot region slightly decreases with decreasing of the barrier width. This decrease is however much smaller for QDs than for superlattice of GaN/AlGaN quantum wells, with thickness similar to the height of QDs. Consequently, the band-to-band transition energies in the vertically correlated GaN/AlN QDs show unexpected, rather weak dependence on the width of AlN barriers. Increasing the QD base diameter leads to stronger decreasing dependence of the band-to-band transition energies vs. the width of AlN barriers, similar to that observed for superlattieces of QWs.

scholarly journals Simple and Multi-layered Quantum dot in various structures

2018 ◽  
Vol 2 (4) ◽  
Author(s):  
Manu Mitra
Keyword(s):  
Quantum Dots ◽  
Wave Function ◽  
Optical Properties ◽  
Quantum Dot ◽  
Three Dimensional ◽  
Polarized Light ◽  
High Peak ◽  
Different Color ◽  
Incoming Light ◽  
Dimensional Wave

Abstract: Quantum dots have interesting optical properties. They absorb incoming light of one color and emit out light of a completely different color. This research paper discloses eigen states of a simple and multilayer quantum dot in various structures for cuboid, cylinder, dome, cone, and pyramid, and its three-dimensional wave function, energy states, light and dark transitions (X-polarized), light and dark transitions (Y-polarized), light and dark transitions (Zpolarized), light and dark transitions (phi = 0 and theta= 45), absorption (phi = 0 and theta = 45), absorption sweep of angle theta, and integrated absorption are plotted and the observations of high peak values are noted and documented.

Theoretical study on nonlinear optical properties of CdS/ZnS spherical quantum dots

Optik ◽  
2019 ◽  
Vol 188 ◽  
pp. 99-103 ◽  
Author(s):  
K. Hasanirokh ◽  
A. Asgari ◽  
M. Mahdizadeh Rokhi
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Nonlinear Optical ◽  
Theoretical Study ◽  
Nonlinear Optical Properties

Size and Piezoelectric Effects on Optical Properties of Self-Assembled InGaAs/GaAs Quantum Dots

2006 ◽  
Author(s):  
M. K. Kuo ◽  
T. R. Lin ◽  
K. B. Hong
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Quantum Dot ◽  
Optical Transition ◽  
Energy Levels ◽  
Three Dimensional ◽  
Dinger Equation ◽  
Element Analysis ◽  
Piezoelectric Effects ◽  
Self Assembled

Size effects on optical properties of self-assembled quantum dots are analyzed based on the theories of linear elasticity and of strain-dependent k-p with the aid of finite element analysis. The quantum dot is made of InGaAs with truncated pyramidal shape on GaAs substrate. The three-dimensional steady-state effective-mass Schro¨dinger equation is adopted to find confined energy levels as well as wave functions both for electrons and holes of the quantum-dot nanostructures. Strain-induced as well as piezoelectric effects are taken into account in the carrier confinement potential of Schro¨dinger equation. The optical transition energies of quantum dots, computed from confined energy levels for electrons and holes, are significantly different for several quantum dots with distinct sizes. It is found that for QDs with the the larger the volume of QD is, the smaller the values of the optical transition energy. Piezoelectric effect, on the other hand, splits the p-like degeneracy for the electron first excited state about 1~7 meV, and leads to anisotropy on the wave function.

VARIATIONAL COMPUTATIONS FOR EXCITONS IN QUANTUM DOTS: A QUANTUM MONTE CARLO STUDY

2011 ◽  
Vol 25 (01) ◽  
pp. 119-130
Author(s):  
A. YILDIZ ◽  
S. ŞAKİROĞLU ◽  
Ü. DOĞAN ◽  
K. AKGÜNGÖR ◽  
H. EPİK ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Monte Carlo ◽  
Ground State ◽  
Quantum Monte Carlo ◽  
Three Dimensional ◽  
Monte Carlo Study ◽  
Wave Functions ◽  
Monte Carlo Techniques ◽  
Oscillator Basis ◽  
Ground State Energies

A study of variational wave functions for calculation of the ground-state energies of excitons confined in a two-dimensional (2D) disc-like and three-dimensional (3D) spherical parabolic GaAs quantum dots (QDs) is presented. We have used four variational trial wave functions constructed as the harmonic-oscillator basis multiplied by different correlation functions. The proposed correlation function formed by including linear expansion in terms of Hylleraas-like coordinates to the Jastrow factor is able to capture nearly exactly the ground-state energies of 3D excitons, and it properly account for the results of 2D excitons. Quantum Monte Carlo techniques combined with the proposed wave function are a powerful tool for studying excitons in parabolic QDs.

Electronic and optical properties of InGaAs/GaAs quantum dots with tunable aspect-ratio

2014 ◽  
Vol 28 (09) ◽  
pp. 1450072
Author(s):  
Pengfei Lu ◽  
Xuxia Zhong ◽  
Chao Sun ◽  
Zhongyuan Yu ◽  
Lihong Han ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Aspect Ratio ◽  
Perturbation Expansion ◽  
Expansion Method ◽  
Equilibrium Composition ◽  
Optimization Method ◽  
Composition Profile ◽  
Wave Functions ◽  
Electronic And Optical Properties

In this paper, a combined approach of finite element method (FEM) and quadratic programming optimization method is proposed to investigate the nonuniform equilibrium composition profile of InGaAs / GaAs quantum dots (QDs) in the framework of Gibbs energy optimization (GEO). The proposed QDs are varied with aspect ratio from 0.3 to 0.5. The wave functions of electron and heavy hole are predicted by using the k ⋅ p method. The changes of wave functions before and after optimization can be observed by using composition optimization. Both the eigenvalues and transition energy change obviously with the increasing aspect ratio. The linear optical absorption coefficients corresponding to the interband ground state transition are obtained via the density matrix approach and perturbation expansion method. The numerical results reveal that the aspect ratio and composition profile play significant roles in determining the electronic and optical properties.

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