First-principles study of the electronic structures and optical properties of C-F-Be doped wurtzite ZnO

The electronic structure and optical properties of pure,C-doped,C-F codoped and C-F-Be clusterdoped ZnO with a wurtzite structure were calculated by using the density functional theory with the plane-wave ultrasoft pseudopotentials method.The results indicate that p-type ZnO can be obtained by C incorporation,and the energy level of C_O above the valence band maximum is 0.36 eV.The ionization energy of the complex Zn₁₆O₁₄CF and Zn₁₅BeO₁₄CF can be reduced to 0.23 and 0.21 eV,individually.These results suggest that the defect complex of Zn₁₅BeO₁₄CF is a better candidate for p-type ZnO.To make the optical properties clear,we investigated the imaginary part of the complex dielectric function of undoped and C-F-Be doped ZnO.We found that there is strong absorption in the energy region lower than 2.7 eV for the C-F-Be doped system compared to pure ZnO.