Lattice constant, bandgap energy, absorption coefficient and dielectric function of the antimony-rich InBixSb1-x alloy using first-principles calculations

So far, little is known about the electronic and optical properties of InBi_xSb_1-x. In this work, the first-principles calculations are performed to research the lattice constant, the bandgap energy, the absorption coefficient and the dielectric function of the antimony-rich InBi_xSb_1-x. The results show that the bowing coefficient for the lattice constant is merely −0.012 Å. According to the band structures, it is found that the Sb-rich InBi_xSb_1-x possesses a direct bandgap at G point. Its bandgap reduction is due to the ascending of the valence band maximum (VBM) and the descending of the conduction band minimum (CBM). For the sake of providing a good description for the bandgap energy in the Sb-rich range, the modified valence band anticrossing (MVBAC) model plus a linear equation is utilized. The result shows that the predicted positive to negative bandgap transition occurs at x = 0.13. Besides, the valence band offset between InSb and InBi is identified to be 0.27eV. For the optical properties, it is found that the Bi component is effective in raising the static dielectric constant of InBi_xSb_1-x. However, it has a minor effect on the transition ability of the electrons. In the Sb-rich component range, the critical point energies $E_0+{\Delta }_0$ $E_1$, $E_1+{\Delta }_1$ $E_2$ and $E_1^{\prime }$ are found to shift toward the low energy direction. The result of the absorption spectra supports this opinion as increasing Bi component leads to a redshift of the absorption spectra. The adjustable bandgap energy and the optical properties of InBi_xSb_1-x demonstrate that it is a strong candidate for fabricating the photodetectors in the 8–12 μm spectral region.