为了研究点缺陷对Al0.5Ga0.5N纳米片电子结构和光学性质的影响, 建立了Al、Ga、N空位和N取代Al、N取代Ga的经典点缺陷结构。基于密度泛函理论的第一性原理超软赝势的方法和GGA-PBE交换互联函数计算了能带、态密度、复介电函数、复折射率、吸收谱和能量损失谱等信息。结果表明, 空位缺陷和替代缺陷会导致带隙变窄, 其中Al空位和Ga空位均使费米能级进入价带, N空位使纳米片显n型性质; 替代缺陷会使纳米片显示半金属性质。在光学性质上, 缺陷导致纳米片复介电函数虚部低能区出现峰值, 说明有电子跃迁的出现。同时空位缺陷导致吸收光谱在低能区有扩展, 可见光范围也包含在内。

In order to study the effects of point defects on electronic structure and optical properties of Al0.5Ga0.5N nanosheets, the classical point defects structures of Al, Ga, N vacancies and N substitute Al and N substitute Ga are established. The method of first-principles ultrasoft pseudopotential based on density functional theory and the GGA-PBE exchange interconnect function are used to calculate the energy band, density of states, complex dielectric function, complex refractive index, absorption spectrum and energy loss spectrum. The results show that the vacancy defects and the substitution defects will lead to the band gap getting narrow. The Al vacancy and the Ga vacancy all make the Fermi level enter the valence band, and the N vacancy makes the nanosheet exhibit n-type properties. The substitution defect will make the nanosheet exhibit semi-metallic properties. In terms of optical properties, the defects lead to produce peaks in the low energy region of the imaginary part of the complex dielectric function of the nanosheet, indicating the occurrence of electronic transitions. At the same time, the vacancy defect causes the absorption spectrum to expand in the low energy region, and the visible light range is also included.