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采用密度泛函理论(DFT)的第一性原理超软赝势方法,计算了缺陷对CdS的电子结构和光电特性的影响。计算电子结构结果表明:CdS是带隙宽带为1.943eV的直接带隙半导体材料。价带主要由S 3p态电子贡献,导带主要由Cd 4d 5s和S3p态电子决定;V_(Cd)缺陷使得Cd_S在G点形成0.867e V的直接带隙;V_S缺陷使得CdS形成隙值为0.948e V的G-M点间接带隙;V_(S-Cd)缺陷使得CdS形成带隙值为0.966eV的K-G点间接带隙;V_(Cd-S)缺陷使得CdS转化为带隙值为0.438e V的n型直接带隙半导体。光学特性计算结果表明:缺陷均使得光学特性向低能方向偏移,同时引起介电常数增加,吸收系数增加,能量损失函数增加。计算结果为CdS光电特性的研发提供理论依据。
The first-principle ultra-soft pseudopotential method of density functional theory (DFT) was used to calculate the effect of defects on the electronic structure and photoelectric properties of CdS. The calculated electronic structure shows that CdS is a direct bandgap semiconductor material with a wide bandgap of 1.943eV. The valence band is mainly contributed by the S 3p state electron. The conduction band is dominated by the Cd 4d 5s and the S3p state electrons. The V_ (Cd) defect makes Cd_S form a direct bandgap of 0.867e V at the G site. The V_S defect makes the CdS formation gap 0.948e V. The V_ (S-Cd) defect makes CdS form an indirect KG gap with a bandgap value of 0.966eV. The Cd-S defect makes CdS transform into a bandgap value of 0.438e V n-type direct bandgap semiconductor. The calculated results of the optical properties show that the defects all shift the optical properties to the low energy direction, and at the same time, the dielectric constant increases, the absorption coefficient increases, and the energy loss function increases. The calculated results provide a theoretical basis for the development of CdS photoelectric properties.