Theoretical Study On Electronic Structures And Optical Properties Of Doped GaAs

GaAs is the most important and the most extensive use Ⅲ-Ⅴ compound semiconductor materials with wide gap, direct band gap, high carrier mobility, low power consumption, radiation resistance, and high temperature resistance. It’s widely applied in the field of microelectronics and optoelectronics because of its excellent optoelectronic characteristics. In recent years, in order to improve its properities and broaden its application field, the reasonable and effective doping is one of the most commonly used methods. With the rapidly development of computational materials science, the theoretical study on electronic and optical properties of doped systems has been an important means. It’s very significant to develop new typical optoelectronic materials.In this paper, the electronic structure and the optical properties of the pure GaAs, Sb-doped GaAs systems and3d transition metals doped GaAs were investigated by using the first-principles pseudopotential approach of the plane wave based on the Density Functional Theory. The main contents are presented as follows:Firstly, we calculate the band structure, density of state and optical properties of the pure zinc blende GaAs. The results indicate that zinc blende GaAs is a direct band gap semiconductor material. The calculation of the band gap0.61eV, compared with the experimental value of1.424eV, has a larger deviation. It’s a common problem existing in the calculations of band gap by DFT method. The calculated band gap is revised by the "scissors" operator and the optical properties obtained after revised agree with the experimental result, which convinced us that our calculation is reliable enough.Afterwards, electronic structure and optical properties of GaAs1-xSbx(x=0,0.25,0.5,0.75,1)have been calculated and the band structure, density of states, complex dielectric function and absorption coefficient have been calculated. The results indicate that Sb doping leads to linearly increasing lattice constants and changing the components of valence and conduction bands of GaAs. The band gap of doped system appears a quadratic polynomial variation tendency. With the increase of the Sb content, the static dielectric constant increased linearly and the absorption wavelength appears an obvious red-shift. The changes of optical properties are qualitatively interpreted in combination with the calculated electronic structure.Finally, the systems of3d transition metals doped GaAs are investigated. The magnetism, half-metallicity and optical properties have been discussed and analysed. By doping3d transition metals in GaAs, the systems show ferromagnetic feature because of the orbital hybrid of3d state of the transition metals and As4p state. The systems of Mn and Cr monodoped GaAs appear obvious half-metallicity, while Fe-doped GaAs shows metallicity. The absorption coefficient of GaAs mono-doped with Mn and Cr produces a new absorption peak at low energy area and the absorption edge are almost in the same position. Comparing with the pure GaAs, the absorption wavelength appears an obvious red-shift. These offer a theoretical basis for the application of doped GaAs in photoelectronics and microelectronics fields.