Structural investigation of Si0.5Ge0.5 alloy for optoelectronic applications: Ab initio study

The structural, electronic and optical properties of the binary silicon–germanium alloy have been investigated using the projector augmented-wave (PAW) calculations with a powerful VASP package (Vienna ab initio simulation package). The structural properties of Si_0.5Ge_0.5 alloy have been calculated using total energy calculations and compared with our empirical model of bulk modulus. The electronic band structure and density of state of Si_0.5Ge_0.5 alloy show that the conduction band minimum (CBM) is located at the X point and the valence band maximum (VBM) is located at the Г point, resulting in indirect (Г–X) energy band gap of 0.48 eV. The results of the refractive index and optical dielectric constant of Si_0.5Ge_0.5 alloy are also obtained. The PAW's results are in good agreement with experimental, theoretical and our model results.