Journal
JOURNAL OF ALLOYS AND COMPOUNDS
Volume 509, Issue 24, Pages 6737-6750Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2011.03.029
Keywords
Optical properties (linear and nonlinear); DFT; FPLAPW
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Funding
- Institute of Physical Biology, UFB [MSM6007665808]
- RDI of the Czech Republic [CZ.1.05/2.1.00/01.0024]
- Grant Agency of the University of South Bohemia [152/2010/Z]
- King Saud University [RGP-VPP-088]
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An all electron full potential linearized augmented plane wave method, within a framework of GGA (EV-GGA) approach, has been used for an ab initio theoretical study of the effect of increasing tellurium content on the band structure, density of states, and the spectral features of the linear and nonlinear optical susceptibilities of the cadmium-selenide-telluride ternary alloys CdSe1-xTex (x = 0.0, 0.25, 0.5, 0.75 and 1.0). Our calculations show that increasing Te content leads to a decrease in the energy band gap. We find that the band gaps are 0.95 (1.76), 0.89 (1.65), 0.83 (1.56), 0.79 (1.44) and 0.76 (1.31) eV for x = 0.0, 0.25, 0.5, 0.75 and 1.0 in the cubic structure. As these alloys are known to have a wurtzite structure for x less than 0.25, the energy gaps are 0.8 (1.6) eV and 0.7 (1.55) eV for the wurtzite structure (x = 0.0, 0.25) for the GGA (EV-GGA) exchange correlation potentials. This reduction in the energy gaps enhances the functionality of the CdSe1-xTex alloys, at least for these concentrations, leading to an increase in the effective second-order susceptibility coefficients from 16.75 pm/V (CdSe) to 18.85 pm/V (CdSe0.75Te0.25), 27.23 pm/V (CdSe0.5Te0.5), 32.25 pm/V (CdSe0.25Te0.75), and 37.70 pm/V (CdTe) for the cubic structure and from 12.65 pm/V (CdSe) to 21.11 pm/V (CdSe0.75Te0.25) in the wurtzite structure. We find a nonlinear relationship between the absorption/emission energies and composition, and a significant enhancement of the electronic properties as a function of tellurium concentration. This variation will help in designing better second-order susceptibility materials by manipulating of the electronic structures of these materials with different compositions to achieve more delocalized atomic bonds. (C) 2011 Elsevier B.V. All rights reserved.
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