GaN(0001)表面电子结构和光学性质的第一性原理研究

First-principles study of the electronic structure and optical properties of GaN(0001) surface

采用基于第一性原理的密度泛函理论平面波超软赝势方法计算了(2×2)GaN(0001)清洁表面的能带结构、态密度、表面能、功函数和光学性质.发现弛豫后GaN(0001)表面的能带结构发生较大变化,表面呈现金属导电特性,导带底附近存在明显的表面态,在偶极矩的作用下表面电荷发生转移,Ga端面为正极性表面;计算获得了GaN(0001)表面的表面能和功函数分别为2.1 J·m^(-2)和4.2 eV;比较分析了GaN(0001)表面和体相GaN的光学性质,发现两者存在较大差异.

The band structure,the density of states,the surface energy,the work function,and the optical properties of GaN（0001）（2×2） clean surface are calculated systematically by the first-principles plane-wave ultro-soft pseudopotential method based on the density function theory.It is found that the band structure of GaN（OOOl） surface changes greatly after relaxation,the surface has metallic conductive properties,and there is obvious surface state near the bottom of conduction band.In the effect of dipole moment,the surface charges shift and Ga-terminated surface is positive polar surface,the surface energy and the work function of GaN（0001） surface are obtained to be 2.1 Jm^（-2） and 4.2 eV,respectively.The optical properties of GaN（0001） surface and bulk phase GaN are analyzed and compared.It is found that there is big difference between them.