ELECTRONIC STRUCTURE OF Si1-xSnx DISORDERED SOLID SOLUTIONS

To help understand the behavior of bowing and related properties of materials, we performed a calculation of the electronic band parameters for series Si1-xSnx 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 Si1-xSnx 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 angstrom for Si and 6.657 angstrom 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 Si1-xSnx alloys exhibits the Vegard behavior yielding the bowing coefficient b = 0.084 angstrom. The band gaps' 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 Si1-xSnx 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.