EXCITON STATES AND INTERBAND TRANSITIONS IN THE DIRECT-GAP Ge/SiGe QUANTUM DOT

2010 ◽  
Vol 24 (12) ◽  
pp. 1191-1197 ◽  
Author(s):  
CONGXIN XIA ◽  
YAMING LIU ◽  
SHUYI WEI
Keyword(s):  
Binding Energy ◽  
Quantum Dot ◽  
Ground State ◽  
Exciton Binding Energy ◽  
Emission Wavelength ◽  
Long Wavelength ◽  
Mass Approximation ◽  
Quantum Size ◽  
Maximum Value ◽  
Sige Quantum Dot

The ground-state exciton binding energy and interband emission wavelength in the direct-gap Ge / SiGe quantum dot (QD) are investigated by means of a variational approach, within the framework of effective-mass approximation. Numerical results show that the ground-state exciton binding energy has a maximum value with increasing quantum size of the direct-gap Ge / SiGe QD. The interband emission wavelength is increased when the QD size is increased. Our results indicate the direct-gap Ge / SiGe QD can be applied for long wavelength optoelectronic devices.

DONOR BOUND EXCITONS CONFINED IN WURTZITE InGaN/GaN QUANTUM DOT NANOWIRE HETEROSTRUCTURES

2013 ◽  
Vol 27 (32) ◽  
pp. 1350186 ◽  
Author(s):  
MIN ZHANG ◽  
JUN-JIE SHI
Keyword(s):  
Binding Energy ◽  
Quantum Dot ◽  
Oscillator Strength ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Exciton Binding Energy ◽  
Optical Transitions ◽  
Mass Approximation ◽  
Nanowire Heterostructures ◽  
The Right

Within the framework of the effective-mass approximation, the donor bound exciton states and interband optical transitions in InGaN / GaN strained quantum dot (QD) nanowire heterostructures (NWHETs) are investigated using a variational method, in which the built-in electric field (BEF) effect due to the spontaneous and piezoelectric polarizations and the three-dimensional (3D) confinement of the electron and hole in the QD are considered. Our results show that the position of the ionized donor, the strong BEF, the In-composition and the QD structural parameters have a significant influence on the donor bound exciton binding energy, the electron interband optical transitions and the exciton oscillator strength. The donor bound exciton binding energy increases obviously if the donor position changes from the left-interface to the right-interface. The BEF reduces the bound exciton binding energy and the exciton oscillator strength. The donor bound exciton binding energy increases, if the In-fraction increases. The emission wavelength monotonically increases if the QD height and radius increase.

EFFECT OF MAGNETIC FIELDS ON BINDING ENERGY OF IMPURITY STATES IN A SEMIMAGNETIC PARABOLIC QUANTUM DOT

2007 ◽  
Vol 21 (17) ◽  
pp. 3035-3044 ◽  
Author(s):  
A. JOHN PETER
Keyword(s):  
Magnetic Field ◽  
Binding Energy ◽  
Quantum Dot ◽  
Mean Field Theory ◽  
Mean Field ◽  
Realistic Model ◽  
Mass Approximation ◽  
Maximum Value ◽  
The Magnetic Field ◽  
Parabolic Quantum Dot

Using a variational approach, the binding energy of shallow hydrogenic impurities in a semimagnetic parabolic quantum dot is calculated within the effective mass approximation. The binding energy is computed for Cd 1-x in Mn x in Te / Cd 1-x out Mn x out Te structures as a function of the dot size in an external magnetic field. The results show that the impurity binding energy (i) increases with the reduction in dot sizes (ii) decreases when the magnetic field is increased for a given dot and (iii) increases to a maximum value at 100 Å and then decreases as the size of the dot increases beyond 100 Å for a realistic model. Spin polaronic shifts are estimated using a mean field theory. These results are compared with the existing literatures.

HYDROGENIC IMPURITY STATES IN WURTZITE ZnO/MgZnO QUANTUM DOT

2010 ◽  
Vol 24 (28) ◽  
pp. 2793-2801
Author(s):  
ZAIPING ZENG ◽  
SHUYI WEI ◽  
JINGBO WEI
Keyword(s):  
Binding Energy ◽  
Quantum Dot ◽  
Electric Field ◽  
Ground State ◽  
Asymmetric Distribution ◽  
Electric Field Effect ◽  
Hydrogenic Impurity ◽  
Mass Approximation ◽  
Donor Binding Energy ◽  
The Right

Based on the effective-mass approximation, considering the built-in electric field effect due to the spontaneous and piezoelectric polarizations, the ground-state donor binding energy of a hygrogenic impurity in a cylindrical wurzite (WZ) ZnO / MgZnO strained quantum dot (QD) is investigated variationally. Numerical results show that the ground-state donor binding energy is highly dependent on the Mg composition, the impurity positions and the QD size. The built-in electric field also induces an asymmetric distribution of the ground-state donor binding energy with respect to the center of the QD. In particular, it is found that the ground-state donor binding energy is insensible to the dot height when the impurity is located at the right boundary of the WZ ZnO / MgZnO strained QD if the dot height is large.

LOCALIZED EXCITONS IN SELF-ASSEMBLED InxGa1-xN QUANTUM DOTS

2005 ◽  
Vol 19 (12) ◽  
pp. 589-598
Author(s):  
XIAN-QI DAI ◽  
FENG-ZHEN HUANG ◽  
JUN-JIE SHI
Keyword(s):  
Quantum Dots ◽  
Binding Energy ◽  
Variational Approach ◽  
Structural Parameters ◽  
Exciton Binding Energy ◽  
Mass Approximation ◽  
Energy Maximum ◽  
Localized Excitons ◽  
The Relationship ◽  
Good Agreement

Within the framework of effective-mass approximation, the exciton states localized in cylindrical InGaN quantum dots (QDs) are investigated using a variational approach. The relationship between the exciton states and structural parameters of QDs with radius R and height L are studied in detail. The numerical results show that the exciton binding energy is sensitive to the ratio of R/L for a QD with a given volume. There is a maximum in the binding energy, where the electrons and holes are the most efficiently confined in the QDs with special structural parameters. The binding energy maximum can be obtained at about L = 1.7 nm for different QD volumes. The exciton binding energy and emission wavelength depend sensitively on structural parameters and the In content in the In x Ga 1-x N active layer. Our calculated emission wavelengths are in good agreement with experimental data.

scholarly journals Оптические спектры кристаллов GaSe и GaS различной толщины

2018 ◽  
Vol 60 (6) ◽  
pp. 1211
Author(s):  
В.Ф. Агекян ◽  
А.Ю. Серов ◽  
Н.Г. Философов
Keyword(s):  
Binding Energy ◽  
High Energy ◽  
Exciton Binding Energy ◽  
Transmission Spectra ◽  
Interband Transitions ◽  
Bulk Crystals ◽  
Quantum Size

AbstractThe transmission spectra of GaSe and GaS crystals of different thicknesses prepared by mechanical stratification of bulk crystals have been investigated. The quantum-size shifts of exciton resonances in thin GaSe samples are as high as 12 meV, which is close to the exciton binding energy. The high-energy interband transitions in GaSe and GaS are observed near 3.4 and 3.7 eV, respectively.

Exact Numerical Procedure for the Binding Energy of Hydrogen Impurities in Quantum Dots with Parabolic Confinements

2013 ◽  
Vol 475-476 ◽  
pp. 1355-1358
Author(s):  
Arnold Abramov
Keyword(s):  
Quantum Dots ◽  
Wave Function ◽  
Binding Energy ◽  
Quantum Dot ◽  
Excited States ◽  
Ground State ◽  
Qualitative Agreement ◽  
Numerical Procedure ◽  
Impurity States ◽  
Parabolic Confinement

In this paper we present exact numerical procedure to calculate the binding energy and wave function of impurity states in a quantum dot with parabolic confinement. The developed method allows control the accuracy of obtained results, as well as calculates the characteristics of not only ground state, but also of the excited states. Comparison of our results with data obtained by other methods is in quantitative and qualitative agreement. We studied the effects of impurity position on the binding energy.

Effects of confined longitudinal optical phonons on the exciton binding energy in a cubic quantum dot

2003 ◽  
Vol 94 (1) ◽  
pp. 437-442 ◽  
Author(s):  
B. El Amrani ◽  
M. Fliyou ◽  
L. Bensaid ◽  
T. Lamcharfi ◽  
K. Rahmani ◽  
...  
Keyword(s):  
Binding Energy ◽  
Quantum Dot ◽  
Longitudinal Optical ◽  
Exciton Binding Energy ◽  
Optical Phonons
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