A comparative study of optical properties of site specific doping in GaNbO4

We have performed ab initio electronic structure calculations on pure and doped GaNbO4, a wide bandgap semiconductor with indirect bangap > 3.0 eV. Our calculations show that sulphur doping reduces the bandgaps and changes the optical properties of GaNbO4. The bandgaps and optical properties are seen to be site dependent. Sulphur doping of GaNbO4 not only enhances the absorbance peaks, but also broadens them in the UV region. Doped and undoped GaNbO4 have less absorbance in comparison with TiO2. Site-2 and Site-3 doping in GaNbO4 shows appearance of the absorbance peaks in the visible light region. The absorbance spectra may show a dopant concentration dependence in addition to site dependence.