AlxGa1-xAs材料结构与物理特性的第一性原理研究

基于密度泛函理论,对Al组分由0~1变化时AlxGa1-xAs体系的晶体结构、差分电荷密度、光电性质以及热力学性质进行第一性原理计算。得到AlxGa1-xAs体系的晶格常数a与Al组分x之间呈线性增加关系。能带结构图显示其禁带宽度将随掺入Al组分x的增加而变大,并且当x≥0.5时,体系能带由直接带隙变为间接带隙。静介电系数ε1(0)随掺入Al组分增加而减小,吸收系数带边随x增大而发生蓝移现象。由材料体系的德拜温度随Al组分的变化情况可知,Al组分增加,体系的声速和弹性劲度常数也相应地增大,高温时比热容的非线性增大是单位质量内AlxGa1-xAs的原胞数非线性增加所导致。通过分析不同Al组分下AlxGa1-xAs体系的光电特征、热力学性质,从而为AlxGa1-xAs在光电子器件以及太阳能电池等方面的应用以及后续的深入研究打下理论基础。

First-principles Study on the Structure and Physical Properties of AlxGa1-xAs Materials

The crystal structure,electron density difference,electronic properties,optical properties and thermodynamic property of AlxGa1-x As system were calculated by the first principle method on the density functional theory as aluminum composition x changes from 0 to 1.The results show that,the lattice constant of AlxGa1-xAs system increases linearly with composition x of aluminum.The band structure shows that,the energy gap width increases with the increase of aluminum composition,and when x≥0.5,the energy gap will change from direct one to indirect one.The coefficient of static dielectric lossε1(0)decrease with the increase of aluminum,and the band edge of the absorption coefficient has blue shifts with the increase of x.It can be seen from the variation of Debye temperature of the material system with the aluminum composition that when aluminum composition increases,the sound velocity and elastic stiffness constants of the system also increase correspondingly.At high temperature,the nonlinear increase of the specific heat capacity is caused by the nonlinear increase of the original cell number of AlxGa1-xAs per unit mass.By analyzing the photoelectric characteristics and thermodynamic property of AlxGa1-x As system with different aluminum atomic composition,the theoretical foundation is laid for the application of AlxGa1-x As semiconductor materials in optoelectronic devices,integrated circuits solar cells and other aspects as well as the subsequent in-depth research.