硅膜厚度对Si/β-FeSi_(2)/Si在宽光谱范围的传输特性影响

Influence of Silicon Film Thickness on the Broadband Transmission Properties of Si/β-FeSi_(2)/Si Structure

分析了β-FeSi_(2)和Si在可见光和近红外(NIR)范围内的复折射率,并设计了由Si和β-FeSi_(2)组成的简单的三层薄膜结构Si/β-FeSi_(2)/Si。顶层硅的厚度是可变的,但中间层β-FeSi_(2)的厚度和底层硅的厚度都是固定的。在可见光和近红外范围内,利用菲涅耳理论和有限元数值分析方法分析了该结构在光垂直入射情况下的光学传输特性,并解释了其物理机制。材料Si在波长0.30~0.37μm范围有巨大的反常色散dn/dλ=30.5μm^(-1),而材料β-FeSi_(2)在波长0.30~1.10μm范围有较大的反常色散dn/dλ=5μm^(-1)。结果表明,这种设计简单的膜层结构可以应用于许多光电器件中,并且反射率和透射率等性能可以通过顶层硅厚度的变化进行灵活调整。当波长在可见光范围和近红外范围内时,该结构的透射率和反射率均有显著差异。

The complex refractive indexes ofβ-FeSi_(2)and Si in the visible and near-infrared(NIR)are analyzed,and the simple structures of three-layer film have been designed.The structures consisting of Si andβ-FeSi_(2)are Si/β-FeSi_(2)/Si with three different parameters.The thickness of Si in the top layer is variable,but both the thickness ofβ-FeSi_(2)in the middle layer and the thickness of Si in the bottom layer are fixed.In the visible and NIR range,both Fresnel theory and the method of finite element numerical analysis have been used to analyze the optical transmission of these structures with normal incidence,and the physical mechanism has been explained.The material Si has a huge anomalous dispersion with about dn/dλ=30.5μm^(-1)in the wavelength range from 0.30μm to 0.37μm,and theβ-FeSi_(2)has larger anomalous dispersion with dn/dλ=5μm^(-1)in the wavelength range from 0.30μm to 1.10μm.The results show that the simple design can be applied in many photodevices,and indicate that the properties,such as reflectivity and transmissivity,can also be flexibly adjusted by changing the thickness of Si in the top layer.When the wavelength is in the visible range or the NIR,the transmissions and reflections of the designs have the sharpest differences,respectively.The structures of the three layer films are straightforward,and their properties have been easily adjusted by changing the thickness of the top Si layer.