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Journal of Physical Studies 23(2), Article 2703 [4 pages] (2019)
DOI: https://doi.org/10.30970/jps.23.2703 ELECTRONIC STRUCTURE OF Si1-xSnx DISORDERED SOLID SOLUTIONSP. M. Yakibchuk, O. V. Bovgyra, M. V.Kovalenko, I. V. Kutsa
Faculty of Physics, Ivan Franko National University of Lviv, 8a, Kyrylo and Mefodiy St., 79005 Lviv, Ukraine |
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To help understand the behavior of bowing and related properties of materials, we performed a calculation of the electronic band parameters for series Si$_{1-x}$Sn$_x$ semiconductor disordered alloys. For this purpose, we have used the model and ab initio pseudopotential plane wave methods within the mixed-atom supercell model of alloys. For band structure calculation of Si$_{1-x}$Sn$_x$ alloys, we used the model pseudopotential (MP) plane wave method. Also, the DFT calculation was performed using the sX-LDA formalism.
Our calculated equilibrium lattice constants are 5.461 \AA\ for Si and 6.657 \AA\ for $\alpha$-Sn, which are consistent with previously reported experimental data and theoretical results. The strong linear relation between the lattice parameters and the composition of Si$_{1-x}$Sn$_x$ alloys exhibits the Vegard behavior yielding the bowing coefficient $b = 0.084$ \AA.
The band gapsХ values at $\Gamma$ and $L$ points decrease with increasing Sn content. The dependence of the $X$-point band gap on Sn compositions exhibits a simplest linear function relation with the correlation coefficient of 0.79754. In contrast, the $L$-point band gaps are highly sensitive to Sn compositions. The calculated indirect-direct band gap crossover in Si$_{1-x}$Sn$_x$ alloys is found to be close to $x = 0.6$, which is extracted from appropriate curve-fitting of $\Gamma$ and $L$ valley band gaps. The corresponding energy gap is $E_g = 0.75$ eV, which is suitable for on-chip optoelectronical devices.
PACS number(s): 71.15.-m, 71.23.-k