Abstract

This study investigates the formation energies, electronic structures, and optical properties of pure and Si-doped ZnO using density functional theory and the Hubbard U (DFT + U_d + U_p) method. The difference in lattice constants between calculated results and experimental measurements is within 1%, and the calculated band gap of pure ZnO is in excellent agreement with experimental values. This study considers three possible Si-doped ZnO structures including the substitution of Si for Zn (Si_s(Zn)), interstitial Si in an octahedron (Si_i(oct)), and interstitial Si in a tetrahedron (Si_i(tet)). Results show that the formation energy of Si_s(Zn) defects is the lowest, indicating that Si_s(Zn) defects are formed more easily than Si_i(oct) and Si_i(tet). All three of the Si defect models exhibited n-type conductive characteristics, and except for the Si_i(oct) mode the optical band gap expanded beyond that of pure ZnO. In both the Si_i(oct) and Si_i(tet) models, a heavier effective mass decreased carrier mobility, and deeper donor states significantly decreased transmittance. Therefore, the existence of interestitial Si atoms was bad for the electric and optical properties of ZnO. View Full-Text