The Effect Of Boron Doping On Optical Properties Of β-SiC

Silicon Carbide (SiC) is a promising semiconducting material because of its excellent physical and electrical properities, such as the wide band gap, high electrical breakdown field, and high thermal conductivity and so on. However, because of its indirect band gap characteristic, the efficiency of photoelectric donversion is very low. Therefore, investing the modification of band gap is great significance. In recent years, with the deeping of theoretical research and experimental technology, researchers prove that the properties of SiC materials can be controlled through the incorporation of impurity.Based on the results of the newest study and a large number of references, we systemly study the heavily B-doped (1×1×1) and (2×2×2) SiC superecells numerically simulating the optical properties of optoelectronic materials, such as dielectric function, reflectivity, energy-loss, absorption and so on. The focuses are causes for the electronic structure and optical properties of undoped and doped SiC. The major work we have done is as follows:First, research status and development trends of SiC are clarified, and the significance of this paper is proposed. The application prospects and fundamental characteristics of SiC are introduced.Second, first-principles based on the density functional theory (DFT) are introduced, and the focal point is the pseudopotential theory. Then we present the CASTEP code in detail.Third, using CASTEP code calculate (1×1×1) and (2×2×2) zinc blende silicon carbide (β-SiC) after Carbon atom replaced by boron atom, and understand the effect of high doping concentration on the electrical structure and the optical properties. The calculated results show that after boron atom substitued Carbon atom the top of thevalence band of B-doped SiC are determined by B2p rather than C2p in SiC; the band gap ofβ-SiC transforms from indirect band gap to direct band gap with band gap shrink; the infrared absorption would intensify with the increase of doping concentration, and absorption edge emerges redshift; the dielectric constant of heavily B-dopedβ-SiC in lowfrequency is found to be remarkably largerFinally, boron on the Carbon and Silicon sites (BC and BSi) (2×2×1) supercellβ-SiC are investigated. Calculation results reveal that except for the difference of electric structures, both dielectric and conductivity spectra of BSi in the infrared region emerge remarkable peak yet BC is relatively flat.This is due to BC apply to Lorentz dispersion theory while BSi is following Drude dispersion theory.