A first principles study of high Bi content in GaSbBi supercell structures for optoelectronic applications

We report the study of structural and optical properties of high Bi content in GaSb supercell leading to the formation of 2х2х1 and 1х2х2 GaSb0.875Bi0.125 supercell structures. This calculation has been performed using the density functional theory (DFT) formalism of Full Potential Linear Augmented Plane Wave (FP-LAPW) method employing WIEN2K package. The minimum volume, bulk modulus, differential pressure and the total energy for both the structures have been investigated under equilibrium conditions. Calculation of optical properties includes absorption, reflection, refraction, extinction co-efficient and the energy losses in both the supercell structures. Phenomenally both the structures are highly stable although the 2х2х1 supercell has a higher compressive flexibility as well as higher total minimum energy in comparison to the 1х2х2 supercell structure. Moreover, the calculated lattice parameters indicate both the structures to be of Zinc Blende in nature. The refractive index and the extinction coefficient values are observed to be higher for 2х2х1 than 1х2х2 supercell structure in the considered incident photon energy range. Significantly, the characteristic curve of refractive index and extinction co-efficient are retraced by the real and imaginary part of the dielectric for both the structures. The optical band gap and maximum optical conductivity has been found to be higher for the 1х2х2 supercell structure in comparison to its counterpart. The reflection and the energy loss characteristic curve are found to be contradictory to one another. The reflectivity coefficient maintains almost a constant value along the incident photon energy range for both the structures; although, the 2х2х1 supercell structure obtains a higher value than the 1х2х2 supercell structure and the vice-versa phenomenon is observed for the energy loss characteristic curve. At higher values of incident photon energy, both the structures attains its distinct plasma frequency values.