First Principles Study Of The Electronic Structure And Optical Properties Of Doped ZnO

The lattice structures, electronic structures and optical properties of pure ZnO and doped ZnO are calculated by first-principle study in this article.The calculated results including lattice structures, band structure, density of states and optical properties show that the supercell of ZnO (2x2x2). ZnO is a direct band gap semiconductor, and the band gap is about 0.72 eV.In the band structure, the valence band consists ofthree parts which are mainly formed of the electrons of O atoms and Zn atoms.For the conduction band, it is primarily derived from the electrons of Zn atoms.For imaginary part of the dielectric function, there are formed three peaks at 1.59,6.49 and 10.25 eV which are due to optical transitions between O and Zn.The optical absorption spectra, reflectivity spectra, refractive index spectra and loss function spectra which are fits very well with the experimental value.The lattice structures, electronic structures and optical properties of Al,Ni doped ZnO and (Al,Ni) codoped ZnO are calculated by first-principle study. For the band structures, Fermi level of Al moves up to the conductor band and formed the n-type semiconductor. Four impurity bands appear in band structure of Ni-ZnO and (Al,Ni)-ZnO, which exhibit n-type conductivity also.The results by calculation reveal that the optical properties of pure ZnO and Al-ZnO, Ni-ZnO, (Al,Ni)-ZnO have a large difference in the low energy range, but are similar in the high energy range.In the visible light range, the absorption coefficient and reflectivity of Al-ZnO are very small but a high transmissivity exists.On the contrary, the two parameters of Ni-ZnO and (Al,Ni)-ZnO are much larger than the other. Moreover, from the optical absorption spectra, it is clearly observed that the Al doped ZnO induces the blue-shift of the optical absorption edge, while Ni-ZnO, (Al,Ni)-ZnO induces the red-shift, and the absorption span of Ni-ZnO, (Al,Ni)-ZnO is bigger than Al-ZnO.The band structure, Mulliken charge overlap population and optical properties of V elements substitute for O site in ZnO structure and five-different-sites of P doped ZnO are calculated by the first-principle method based on density functional theory. In the sttucture of N, P, As, Sb doped ZnO, they are all p-type conductivity. The P-ZnO and As-ZnO have a similar electronic structure.In the five-different-sites of P doped ZnO, Pâ…¡-ZnO exhibits p-type conductivity. The final enthalpy of Pâ…¢-ZnO is lowest and the structure is the most stable one.The optical properties of five-different-sites of P doped ZnO are obviously different in the low energy range, while similar in the high energy range.In the low energy range, Pâ…¢-ZnO has the biggest absorption coefficient and reflectivity, which means a higher transmissivity in the visible light range.The results for Pâ… -ZnO are opposite to that of Pâ…¢-ZnO.