Electronic structure and optical properties of In-doped SrTiO₃ by density function theory

The effect of In doping on the electronic structure and optical properties of SrTiO_3 is investigated by the first-principles calculation of plane wave ultra-soft pseudo-potential based on the density function theory (DFT). The calculated results reveal that due to the hole doping, the Fermi level shifts into valence bands (VBs) for SrTi_1-xIn_xO_3 with x=0.125 and the system exhibits p-type degenerate semiconductor features. It is suggested according to the density of states (DOS) of SrTi_0.875In_0.125O_3 that the band structure of p-type SrTiO_3 can be described by a rigid band model. At the same time, the DOS shifts towards high energies and the optical band gap is broadened. The wide band gap, small transition probability and weak absorption due to the low partial density of states (PDOS) of impurity in the Fermi level result in the optical transparency of the film. The optical transmittance of In doped SrTiO_3 is higher than 85% in a visible region, and the transmittance improves greatly. And the cut-off wavelength shifts into a blue-light region with the increase of In doping concentration.