第一性原理研究[112]硅锗异质结纳米线的电子结构与光学性质
First-principles study on the electronic structure and optical properties of [112] Si/Ge heterostructure nanowires

基于密度泛函理论体系下的广义梯度近似，本文利用第一性原理方法着重研究了[112]晶向硅锗异质结纳米线的电子结构与光学性质．能带结构计算表明：随着锗原子数的增加，[112]晶向硅锗纳米线的带隙逐渐减小；对Si36Ge24H32纳米线施加单轴应变，其能量带隙随拉应变的增加而单调减小．光学性质计算则表明：随着锗原子数的增加，[112]硅锗纳米线介电函数的峰位和吸收谱的吸收边均向低能量区移动；而随着拉应变的增大，吸收系数峰值呈现出逐渐减小的趋势，且峰位不断向低能量区移动，上述结果说明锗原子数的增加与施加拉应变均导致[112]硅锗纳米线的吸收谱产生红移．本文的研究为硅锗异质结纳米线光电器件研究与设计提供一定的理论参考．
Based on the generalized gradient approximation of density functional theory (DFT), the electronic structures and optical properties of [112] Si/Ge heterojunction nanowires are investigated by using first-principles calculations. Band structure calculations show that the bandgap of [112] Si/Ge nanowire decreases with the increase of the number of germanium atoms. When uniaxial strain is applied to Si36Ge24H32 nanowire, the energy bandgap monotonically decreases with the increase of tensile strain. The calculated optical properties display that both the peak of dielectric constant and the absorption edge of absorption spectrum of [112] Si/Ge nanowire move to the low energy region with the increase of the number of germanium atoms. Meanwhlie, the peak value of absorption coefficient shows a decreasing trend with the increase of tensile strain, and the peak position continuously moves to the low energy region. The above results indicate that both the increase of germanium atom number and the applied tensile strain cause the red shift of the absorption spectrum of [112] Si/Ge nanowire. Our study provides some theoretical references for the research and design of Si/Ge nanowire-based optoelectronic devices.