摘要:
硅表面固有的菲涅耳反射,使得硅基半导体光电器件(如太阳能电池、红外探测器)表面有30%以上的入射光因反射而损失掉,严重影响着器件的光电转换效率。寻找一种方法降低硅基表面的反射率,进而提高器件的效率成为近年来研究的重点。本文基于纳米压印光刻技术,在2英寸单晶硅表面制备出周期530 nm,高240 nm的二维六角截顶抛面纳米柱阵列结构。反射率的测试表明,当入射光角度为8?时,有纳米结构的硅片相对于无纳米结构的硅片来讲,在400到2500 nm波长范围内的反射率有很明显的降低,其中,800到2000 nm波段的反射率都小于10%,在波长1360 nm附近的反射率由31%降低为零。结合等效介质理论和严格耦合波理论对结果进行了分析和验证。
Abstract:
The intrinsic Fresnel reflection of Si surface, which causes more than 30%of the incident light to be reflected back from the surface, seriously influences the photoelectric conversion efficiency of Si-based semiconductor photoelectric device, such as solar cell and infrared detector. Recently, how to find a simple and efficient method, which is also suitable for mass production, aiming to suppress the undesired reflectivity and therefore improving the efficiency of the device, has become a research focus. In this work, we successfully convert a 2D nanopillar array structure into the Si surface via the nanoimprint lithography. The nanopillar has a flat surface and a paraboloid-like side wall profile. The period and the height of the hexagonal array structure are 530 nm and 240 nm, respectively. The cut-paraboloid nanopillar structure generates a relatively smooth gradient of the refractive index in the optical interface, which plays a key role in suppressing the Fresnel reflection in a wide range of wavelength. The reflectivity of the nanopillar arrayed Si surface is tested in a wavelength range from 400 to 2500 nm at an incident angle of 8?during the measurement. Compared with the unstructured Si, the structured Si has a reflectivity that significantly decreases in the test area: in a wavelength range from 400 to 1200 nm, and the reflectivity of the silicon surface is less than 10%. Specifically, the reflectivity is almost zero at a wavelength of about 1360 nm. The results are confirmed with the effective medium and rigorous coupled-wave theory.
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