GaN(0001)表面台阶结构的第一性原理研究

First-principle Studies of GaN(0001)Surface with Step Structure

半导体表面的研究对了解半导体材料的表面形貌、原子结构、材料生长以及电学性质等具有重要意义,其中半导体表面的台阶结构对材料生长起着重要的作用。基于密度泛函理论的第一性原理计算方法,对GaN(0001)表面台阶的原子构型和电子结构等性质进行了计算。对符合化学计量比的(Ga2,N1)台阶进行结构优化后发现,GaN表面Ga原子出现向上向下交替弛豫现象。电荷密度分布图和能带结构结果表明,向上弛豫的Ga原子出现电荷分布,其能带处于费米能级以下,向上弛豫的Ga原子贡献表面态。部分态密度结果表明,不同的台阶边缘具有不同的性质,因此导致带隙中不同特征带的出现。

The study of semiconductor surfaces is important for understanding the surface morphology,atomic structure,material growth,and electrical properties of semiconductor materials,where the step structure of semiconductor surfaces plays an important role in material growth.The atomic and electronic structures properties of the step structure of GaN(0001)were investigated by employing first-principle calculations based on density functional theory in this paper.After structural optimization of the(Ga2,N1)step that conforms to the stoichiometric ratio,it is found that the structure optimization causes the Ga atoms on the GaN(0001)surface relax up and down alternately.The charge density distribution and the band energy indicate that the upwardly relaxed Ga atoms cause surface states inside the energy bands.As the upwardly relaxed Ga atoms show charge distribution and their energy bands are below the Fermi energy level.The partial charge density shows that different step edges have distinct properties,thus resulting in the emergence of different feature bands in the band gap.