掺杂和应变对硅纳米线电子结构与光学性质的调制影响

为了研究掺杂和应变对[111]晶向硅纳米线的电子结构与光学性质的调制影响,基于密度泛函理论体系下的广义梯度近似(general gradient approximation，GGA),采用第一性原理方法开展了相关计算。能带计算表明：空位掺杂和元素掺杂均引入杂质能级,形成了N型和P型半导体材料。单轴应变则进一步减小了带隙,增强了掺杂硅纳米线的导电性,但由于应变也修饰了费米面附近能级的形貌,能带曲率突变影响了体系的导电性能。光学性质计算表明：相比于空位掺杂,元素掺杂更有效地改变了SiNWs的介电函数、吸收系数、折射率与反射率等光学参数,而单轴应变则削弱了元素掺杂的影响。拉应变提升了光吸收的范围和强度,尤其是可见光波段,使掺杂硅纳米线成为优质光伏材料,压应变则降低了对紫外光波段的吸收效率。在紫外区域,拉应变和压应变对掺杂硅纳米线的折射率与反射率的影响相反,在红外和可见光区域影响则一致。本文研究结果为基于应变和掺杂硅纳米线的光电器件设计与应用提供一定的理论参考。

The effects of doping and strain on the electronic structure and optical properties of silicon nanowires

In order to study the influence of doping and strain on the electronic structure and optical properties of [111] crystal-oriented silicon nanowires, based on the generalized gradient approximation (GGA) under the density functional theory system, the first-principles method was used to carry out related calculations. Energy band calculations show that both vacancy doping and element doping introduce impurity energy levels, which change the band gap of SiNWs and form N-type and P-type semiconductor materials. Uniaxial strain further reduces the band gap and strongly enhances the conductivity, but it also modifies the morphology of the energy levels near the Fermi surface. The sudden change in band curvature also affects the conductivity of doped SiNWs. The calculation of optical properties shows that compared with vacancy doping, element doping more effectively changes the dielectric function, absorption coefficient, refractive index and reflectivity of SiNWs, while uniaxial strain weakens the effect of element doping. The tensile strain increases the range and intensity of light absorption, especially in the visible light band, making doped silicon nanowires as a high-quality photovoltaic material, while compressive strain reduces the absorption efficiency in the ultraviolet light band. In the ultraviolet region, tensile strain and compressive strain have opposite effects on the refractive index and reflectivity of doped silicon nanowires, and the effects are the same in the infrared and visible regions The results of this paper provide a theoretical reference for the design and application of optoelectronic devices based on strained and doped silicon nanowires.