Excited states of two-dimensional excitons in quantum wells

2002 ◽  
Vol 80 (7) ◽  
pp. 781-786
Author(s):  
Y P Varshni
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Excited States ◽  
Coulomb Interaction ◽  
Two Dimensional ◽  
Wkb Method ◽  
Electron Hole ◽  
Free Carriers ◽  
Screening Parameter ◽  
Electron Hole Pair

The energies of ten excited states of screened two-dimensional excitons in a semiconducting quantum-well structure are calculated as a function of the screening parameter qs by the WKB method. The screening of the Coulomb interaction between the electron–hole pair by the free carriers present is taken into account by using the screened potential obtained by Stern and Howard (1967). The energies of the excited states are found to decrease with increasing values of the screening parameter qs in all cases. Further the levels become unbound at finite values of the screening parameter. Critical screening parameters are estimated for the ten states. PACS Nos.: 73.21Fg, 78.67De, 71.35-y, 71.35Cc

scholarly journals Auger Recombination in Quantum Well Laser with Participation of Electrons in Waveguide Region

2018 ◽  
Vol 57 (2) ◽  
pp. 193-198
Author(s):  
A.A. Karpova ◽  
D.M. Samosvat ◽  
A.G. Zegrya ◽  
G.G. Zegrya ◽  
V.E. Bugrov
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Auger Recombination ◽  
Nonradiative Recombination ◽  
Electron Hole ◽  
Quantum Well Laser ◽  
Semiconductor Quantum Wells ◽  
Electron Hole Pair ◽  
Quantum Well Width ◽  
Nonequilibrium Carriers

Abstract A new mechanism of nonradiative recombination of nonequilibrium carriers in semiconductor quantum wells is suggested and discussed. For a studied Auger recombination process the energy of localized electron-hole pair is transferred to barrier carriers due to Coulomb interaction. The analysis of the rate and the coefficient of this process is carried out. It is shown, that there exists two processes of thresholdless and quasithreshold types, and thresholdless one is dominant. The coefficient of studied process is a non-monotonous function of quantum well width having maximum in region of narrow quantum wells. Comparison of this process with CHCC process shows that these two processes of nonradiative recombination are competing in narrow quantum wells, but prevail at different quantum well widths.

Ti3C2-MXene/Bismuth Ferrite Nanohybrids for Efficient Degradation of Organic Dye and Colorless Pollutant

2019 ◽  
Author(s):  
Ayesha Tariq ◽  
M. Abdullah Iqbal ◽  
S. Irfan Ali ◽  
Muhammad Z. Iqbal ◽  
Deji Akinwande ◽  
...  
Keyword(s):  
Surface Area ◽  
Low Cost ◽  
Bismuth Ferrite ◽  
Organic Dye ◽  
Two Dimensional ◽  
Electron Hole ◽  
Photocatalytic Application ◽  
Electron Hole Pair ◽  
Pair Generation ◽  
Photocatalytic Applications

<p>Nanohybrids, made up of Bismuth ferrites/Carbon allotropes, are extensively used in photocatalytic applications nowadays. Our work proposes a nanohybrid system composed of Bismuth ferrite nanoparticles with two-dimensional (2D) MXene sheets namely, the BiFeO<sub>3</sub> (BFO)/Ti<sub>3</sub>C<sub>2</sub> (MXene) nanohybrid for enhanced photocatalytic activity. We have fabricated the BFO/MXene nanohybrid using simple and low cost double solvent solvothermal method. The SEM and TEM images show that the BFO nanoparticles were attached onto the MXene surface and in the inter-layers of two-dimensional (2D) MXene sheets. The photocatalytic application is tested for the visible light irradiation which showed the highest efficiency among all pure-BFO based photocatalysts, i.e. 100% degradation in 42 min for organic dye (Congo Red) and colorless aqueous pollutant (acetophenone) in 150 min, respectively. The present BFO-based hybrid system exhibited the large surface area of 147 m<sup>2</sup>g<sup>-1</sup>measured via Brunauer-Emmett-Teller (BET) sorption-desorption technique, and is found to be largest among BFO and its derivatives. Also, the photoluminescence (PL) spectra indicate large electron-hole pair generation. Fast and efficient degradation of organic molecules is supported by both factors; larger surface area and lower electron-hole recombination rate. The BFO/MXene nanohybrid presented here is a highly efficient photocatalyst compared to other nanostructures based on pure BiFeO<sub>3</sub> which makes it a promising candidate for many future applications.</p>

Effect of well thickness on the two-dimensional electron-hole system inAlxGa1−xSb/InAs quantum wells

1997 ◽  
Vol 55 (20) ◽  
pp. 13677-13681 ◽  
Author(s):  
Ikai Lo ◽  
Jih-Chen Chiang ◽  
Shiow-Fon Tsay ◽  
W. C. Mitchel ◽  
M. Ahoujja ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Electron Hole

Intersubband Transitions in In0.07Ga0.93As/Al0.4Ga0.6As Multiple Quantum Wells

1994 ◽  
Vol 299 ◽  
Author(s):  
F. Szmulowicz ◽  
M. O. Manasreh ◽  
C. Kutsche ◽  
C. E. Stutz
Keyword(s):  
Energy Level ◽  
Quantum Well ◽  
Quantum Wells ◽  
Excited States ◽  
Fermi Energy ◽  
Multiple Quantum Well ◽  
Energy Separation ◽  
Multiple Quantum ◽  
Fermi Energy Level ◽  
Intersubband Transitions

AbstractIntersubband transitions in a series of well-doped ([Si] = 2.0×1018cm−3) In0.07Ga0.93As/Al0.4Ga0.6As multiple quantum well samples were studied as a function of the well width by using the optical absorption technique. A single intersubband transition is observed in samples in which the Fermi energy level is between the ground and the first excited states in the quantum well. On the other hand, two intersubband transitions were recorded in samples where the Fermi energy level lies between the first and the second excited states. These two intersubband transitions were attributed to ground-to-first excited states and first-to-second excited states transitions. The energy separation between the latter two intersubband transitions was found to increase as the well width is increased. The fact that two intersubband transitions were observed in certain samples may suggest that specially designed quantum wells can be used for two color long wavelength infrared detectors.

Electronic Properties of Ultrathin Isoelectronic Intralayers in Semiconductors

1991 ◽  
Vol 240 ◽  
Author(s):  
K. A. Mäder ◽  
A. Baldereschi
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Green’S Function ◽  
Electronic Properties ◽  
Green's Function ◽  
Tight Binding ◽  
Function Approach ◽  
Diamond Structure ◽  
Two Dimensional ◽  
Host Materials

ABSTRACTAn empirical tight-binding Koster-Slater approach is used to determine the electronic properties of ultrathin“quantum wells”in semiconducting host materials of the zincblende or diamond structure. The“quantum well”is viewed as a giant two-dimensional isoelectronic impurity, and treated in a perturbational Green's function approach. We present results on the AlAs/GaAs and on the InP/InAs systems.

scholarly journals Evaluation of Energy and Density of States of Two Dimensional Quantum Structure (Quantum Well)

2018 ◽  
pp. 1-6
Author(s):  
J. Ilouno ◽  
I. J. Audu ◽  
M. Y. Mafuyai ◽  
N. Okpara
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Density Of States ◽  
High Energy ◽  
Two Dimensional ◽  
Density Of State ◽  
Quantum Structure ◽  
Electrochromic Devices ◽  
High Energy Level ◽  
System Designs

Quantum structures (e.g. quantum wells) are a critical part of optical system designs (lasers, modulators, switches etc.). In the quantum well, the motion of the particle is quantized in one direction while the particle moves freely in other two directions. The density of state of the quantum structure is the possible number of state an excited electron can occupy per unit volume. The density of state depends on the energy at which the electron moves when excited. In this paper, the energy and density of states of two-dimensional quantum structure (quantum well) were calculated. The results obtained revealed the density of state increases with the energy but exhibited maximum and minimum peaks. Maximum peaks occurred at 4 eV and 7.5 eV while the minimum peaks occurred at 5 eV and 8 eV. These show that energy of state for quantum wells neither varies linearly nor exponentially with a density of state because of high energy level. The findings are in agreement with published literature. Some applications of quantum wells include: bioconjugates, solar cells, photovoltaic, photo and electrochromic devices etc.

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