基于非金属等离激元材料的硅基近红外热载流子转换研究

In the past few years, metallic nanosystems have been demonstrated as a promising strategy for photoelectric conversion via the nonradiative decay of surface plasmons (SPs) to hot carriers at the metal-semiconductor (M-S) interface. Based on intra-band transitions of the SPs materials, this hot carrier-mediated photon harvesting mechanism can be incorporated into a Silicon (Si) platform and provides significantly extended response beyond the silicon cut-off wavelength, without the limitations imposed by band-to-band transitions of semiconductors. Thus, the hot carrier-mediated photoelectric conversion of SPs materials could benefit the development of Si-based large-array near-infrared (NIR) photoelectric conversion devices, ease of monolithic integration of the NIR optoelectronics with Si electronics, and also can enhance photocatalytic performance. However, since the in metal-based SPs materials intrinsically possess high free-electron density and their electron density of states are difficult to manipulate, the generated hot carriers suffer from serious energy loss during the transport and emission processes due to the electron-electron scattering and energy mismatch with the M-S junction. As alternatives to conventional metal-based SPs materials, the newly developed non-metallic SPs materials offer many advantages, including the tunability of optical constants and electronic band structures, Epsilon-Near-Zero (ENZ) effect and high mobility of carriers. To this end, we propose herein to incorporate the non-metallic SPs materials into the Si-based NIR hot carrier conversion: To realize more efficient light coupling and carrier transport simultaneously, we will adopt ENZ effect to achieve perfect light trapping in ultrathin film; A comprehensive analysis and considerations of the electronic band structures and electron density of states of the non-metallic SPs materials will be included, through which the best composition of the materials for efficient suppression of the emission losses associated to the energy mismatch between the hot carrier and M-S barrier; Coupled electrical-thermal-electrical multi-physics will also be explored to evaluate the different conversion mechanisms involving in the energy dissipation processes of the hot carriers. Through this project, we hope to demonstrate the feasibility of using non-metallic SPs materials for more efficient NIR hot carrier-mediated photoelectric conversion on Si platform.

近年来，金属纳米体系借助表面等离激元(SPs)非辐射衰减在金属-半导体(MS)界面热载流子发射行为展现了一类潜在高效光电转换机制。由于不受半导体带间跃迁限制，基于该机制可在硅基上实现硅带隙内近红外光子能量捕捉，利于硅基大面阵近红外光电转换、单片硅光电子器件互联和光催化应用。然而金属SPs材料电子浓度极高且电子态密度难以调控，导致热载流子在传输和发射过程因电子-电子散射和结发射能量失配而面临严重能量损耗。新兴起的非金属SPs材料具有光学常数和电子能带可调、ENZ效应和高迁移率等优势。本项目拟开展非金属SPs材料的硅基近红外热载流子转换研究：利用ENZ效应实现超薄膜层光场局域和高吸收，提高热载流子产率同时抑制其传输损耗；借助电子能带和态密度分析优化材料组分，从材料本质上减小热载流子发射能量失配；光热电多物理场耦合下研究热载流子转换中的多种并存机制，最终实现硅基上更加高效的热载流子红外光电转换。

金属纳米体系借助表面等离激元(SPs)非辐射衰减在金属-半导体(MS)界面热载流子发射行为展现了一类潜在高效光电转换机制。由于不受半导体带间跃迁限制，基于该机制可在硅基上实现硅带隙内近红外光子能量捕捉，利于硅基大面阵近红外光电转换、单片硅光电子器件互联和光催化应用。然而金属SPs材料电子浓度极高且电子态密度难以调控，导致热载流子在传输和发射过程因电子-电子散射和结发射能量失配而面临严重能量损耗。新兴起的非金属SPs材料具有光学常数和电子能带可调、ENZ效应和高迁移率等优势。. 本项目了探索非金属半导体作为SPs材料用于实现的硅基近红外热载流子转换研究,利用ENZ效应实现超薄膜层光场局域和高吸收，提高热载流子产率同时抑制其传输损耗；借助电子能带和态密度分析优化材料组分，从材料本质上减小热载流子发射能量失配，最终实现了硅基上更加高效的热载流子红外光电转换。. 本项目中我们取得以下研究成果：.1）制备高质量TCO薄膜，在1100-2500 nm波长范围内展示了较好的ENZ特性；.2）提出并实现了多种高效ENZ耦合光学结构,实现超薄TCO的理想吸收(A>90%)；.3）研制了基于ENZ特性的TCO/Si红外探测器，1300nm处响应度大于27 mA/W，响应带宽1100-2500 nm。