First - Principles Calculation Of The Electronic Structure And Optical Properties Of The Si - Doped Si 2 Si

The alkaline-earth metal of Ca2 Si is a Kankyo Semiconductor with a direct band gap. It has excellent optoelectronic properties such as, high carrier mobility, low consumed power, radiation resistance, high temperature resistant etc. In this paper, the electronic structure and optical properties of Ca2 Si, P-doping Ca2 Si, the defect of Ca2 Si and the anisotropic strain on Ca2P0.25Si0.75 have been calculation by the first-principle pseudo-potential method based on density functional theory(DFT) for improve its perfoemance and broaden its application fields. The main studies are summarized as follows:Firistly, the energy band structure, density of states and optical properties of Ca2 Si have been calculated systemically by density function theory of the first-principles pseudo potential method. The results show that Ca2 Si is a direct semiconductor and the band gap is 0.299 eV.Secondly, the energy band structure, density of states, density of states, complex dielectric function, complex refractive index, reflectivity, absorption, conductivity and energy loss function of Ca2PxSi1-x(x=0, 0.0625, 0.125, 0.1875, 0.25, 0.3125, 0.4375, 0.5) have been systemically the first-principles pseudo potential method based on density functional. The results showed that the composition of the conduction band and valence band of Ca2PxSi1-x were transformed by doping. The lattice constant of Ca2PxSi1-x has linear decreased with the increasing of P impurity concentration. The energy band structure of Ca2PxSi1-x has linear changed with the changing of P impurity concentration. The optical properties have a significantly changed: the static dielectric function increased and the absorption red-shifted with the increasing of P impurity concentration. In this thesis we explained qualitatively the mechanism of the optical properties of Ca2PxSi1-x using the P impurity induced electric structure of Ca2 Si.Thirdly, the energy band structure of different types of defects on Ca2 Si has been calculated systemically by function theory of the first-principles pseudo potential method. The results showed that the orthogonality Ca2 Si into a conductor by implement the defect. The lattice constant of cubic Ca2 Si has change, and the composition of the conduction band and valence band of Ca2 Si were transformed by inplement the defect.Finally, the energy band structure, density of states, density of states, complex dielectric function, complex refractive index, reflectivity, absorption, conductivity and energy loss function of the isotropic strian on Ca2P0.5Si0.75 have been calculated systemically by function theory of the first-principles pseudo potential method. The changing mechanism of the electric structure and optical properties of Ca2P0.5Si0.75 under the isotropic strain are analyzed. The influencing mechanism of the electric structure and optical properties under the isotropic strain are revealed. Provide the theoretical basis of Ca2P0.5Si0.75 for crystal growing and performance improvement.