硫钝化GaP(001)表面的结构及电学性质研究

Structural and Electronic Properties of Sulfur Passivation of GaP(001) Surface

基于第一性原理的密度泛函理论,分析了覆盖度为1 ML(monolayer)的硫吸附在磷截止和镓截止的GaP(001)(1×2)表面的结构和电学属性。能量计算表明,最稳定的吸附模型均是SHB+ST4,镓和磷二聚物都被断开,周期单元由(1×2)变成(1×1),硫原子吸附在桥位置,Ga-S键比P-S键更稳定。电学性质分析可知,硫吸附在镓截止GaP表面后能隙中的表面态大幅度减少,而吸附在磷截止的表面时表面态并没有减少且在0.74 eV处多了一个新峰,硫吸附在镓截止表面后的态密度分布与实验结果吻合很好。因此,1 ML的硫吸附在GaP(001)面时表面上最主要形成Ga-S键。

Using first-principles total energy method, the structural and electronic properties of Ga- and P-terminated GAP（001） （1 × 2） surfaces adsorbed with a monolayer of sulfur were studied. Total energy calculations show that all dimers are broken and the periodicity becomes （1× 1）. Sulfur atoms occupy bridge sites on both Ga- and P-terminated surfaces. The S--Ga bond is stronger than the S--P bond. The electronic analysis indicated that the surface state within the energy gap on the Ga-terminated GaP surface was noticeably reduced by the sulfur adsorption, while the reduction did not occur on the P-terminated surface and a new peak existed at 0.74 eV. DOS analysis of the Ga-terminated surface agrees well with the experiments. Thus, it is suggested that the S--Ga bonds are dominantly formed at the S-covered GAP（001） surface.