Dependence of the Absorption Spectra of III-V Semiconductor Quantum Dots on the Size Distribution

2007 ◽  
Vol 31 ◽  
pp. 59-61
Author(s):  
Subindu Kumar ◽  
Dipankar Biswas ◽  
Tapas Das
Keyword(s):  
Quantum Dots ◽  
Optical Absorption ◽  
Size Distribution ◽  
Absorption Spectra ◽  
Gaussian Function ◽  
Semiconductor Quantum Dots ◽  
Optical Absorption Spectra

In recent years there have been extensive studies on III-V semiconductor quantum dots (QDs). In this paper we have formulated the absorption spectra of a realistic QD system with dot size distribution described by a Gaussian function. The dots were approximated as cubic boxes having finite potentials at the boundaries. The effects of size non uniformity on the optical absorption spectra of a realistic QD system was analyzed and the results have been compared with ideal dots having infinite potentials at the boundaries.

QUANTUM CONFINEMENT AND COULOMB EFFECTS IN SEMICONDUCTOR QUANTUM DOTS

1990 ◽  
Vol 04 (16) ◽  
pp. 1009-1016 ◽  
Author(s):  
Y.Z. HU ◽  
S.W. KOCH ◽  
D.B. TRAN THOAI
Keyword(s):  
Quantum Dots ◽  
Optical Absorption ◽  
Absorption Spectra ◽  
Quantum Confinement ◽  
Semiconductor Quantum Dots ◽  
Optical Absorption Spectra ◽  
Electron Hole ◽  
Quantum Confinement Effects ◽  
Electron Hole Pair ◽  
Coulomb Effects

Coulomb and quantum confinement effects in small semiconductor microcrystallites are analyzed. Energies and wavefunctions for one- and two-electron-hole-pair states are computed and optical absorption spectra are evaluated.

scholarly journals Electronic characteristics of CdS quantum dots with defects

2020 ◽  
pp. 28
Author(s):  
I. M. Kupchak ◽  
D. V. Korbutyak ◽  
N. F. Serpak
Keyword(s):  
Quantum Dots ◽  
Optical Absorption ◽  
Valence Band ◽  
Absorption Spectra ◽  
Density Functional ◽  
Optical Absorption Spectra ◽  
Cds Quantum Dots ◽  
Generalized Gradient ◽  
Substitutional Impurity ◽  
Cadmium Vacancy

Using the density functional theory and the generalized gradient approximation, we calculated the atomic structure, the density of electronic states, and the optical absorption spectra of CdS quantum dots containing intrinsic defects — a cadmium vacancy VCd and an interstitial sulfur atom SI, and substitutional impurities — zinc and copper in place of the atom cadmium — ZnCd and CuCd, respectively. The calculations were performed for the Cd33S33 cluster corresponding to the so-called “magic” size of the quantum dot. This size has a minimum of dangling bonds at the surface and allows the using of such a cluster without the passivation. The structural relaxation during the formation of such defects and the distribution of the wave function of the state corresponding to the top of the valence band are analyzed in details. It has been shown that the cadmium vacancy forms local states in the band gap of CdS nanocrystals, and can serve as centers of radiative recombination. Other defects form energy levels in the depths of the valence band or near its top, but whose energy positions do not correspond to the band maxima in the experimental photoluminescence spectra of CdS quantum dots, both undoped and doped with zinc. The calculated optical absorption spectra demonstrate a strong peak in the region of fundamental absorption of CdS for a cluster containing a substitutional impurity of CuCd, in contrast to other systems where no such peaks are observed. In addition, the replacement of the cadmium atom with copper leads to a decrease in the number of chemical bonds to three and, accordingly, to the largest relaxation among the systems studied. This feature is caused by the crystal structure inhomogeneity of copper sulfide CuxS, which, depending on stoichiometry, can be either a semiconductor or a metal.

DEPENDENCE OF THE ABSORPTION SPECTRA OF III–V SEMICONDUCTOR QUANTUM DOTS ON THE FUNDAMENTAL PARAMETERS

2010 ◽  
Vol 09 (04) ◽  
pp. 345-349 ◽  
Author(s):  
SUBINDU KUMAR ◽  
SANJIB KABI
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Band Gap ◽  
Size Distribution ◽  
Absorption Spectra ◽  
Density Of States ◽  
Semiconductor Quantum Dots ◽  
Band Offset ◽  
Fundamental Parameters

The absorption spectra of semiconductor quantum dots (QDs) are expected to be a series of δ-function-like discrete lines due to the nature of the density of states. In a realistic III–V QD system, the absorption spectra is the superimposition of the contribution from each individual dot and the overall behavior is modeled by considering a Gaussian size distribution. In this paper, we study and present the dependence of the Gaussian nature of the absorption spectra of In X Ga 1-X N/GaN QD systems on the dot size distribution and some fundamental parameters such as bowing effect of the band gap, band offset ratio, and so on. It is observed that the absorption spectra depend strongly on the dot size distribution. The results presented helps to get a better insight of the optical properties of In X Ga 1-X N/GaN QD systems.

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