Su Zih-Chun, Li Yu-Hao, Lin Ching-Fuh
Graduate Institute of Photonics and Optoelectronics, The Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan.
Graduate Institute of Electronics Engineering, The Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan.
Nanomaterials (Basel). 2022 May 20;12(10):1750. doi: 10.3390/nano12101750.
Infrared detection technology has been widely applied in many areas. Unlike internal photoemission and the photoelectric mechanism, which are limited by the interface barrier height and material bandgap, the research of the hot carrier effect from nanometer thickness of metal could surpass the capability of silicon-based Schottky devices to detect mid-infrared and even far-infrared. In this work, we investigate the effects of physical characteristics of Cr nanometal surfaces and metal/silicon interfaces on hot carrier optical detection. Based on the results of scanning electron microscopy, atomic force microscopy, and X-ray diffraction analysis, the hot carrier effect and the variation of optical response intensity are found to depend highly on the physical properties of metal surfaces, such as surface coverage, metal thickness, and internal stress. Since the contact layer formed by Cr and Si is the main role of infrared light detection in the experiment, the higher the metal coverage, the higher the optical response. Additionally, a thicker metal surface makes the hot carriers take a longer time to convert into current signals after generation, leading to signal degradation due to the short lifetime of the hot carriers. Furthermore, the film with the best hot carrier effect induced in the Cr/Si structure is able to detect an infrared signal up to 4.2 μm. Additionally, it has a 229 times improvement in the signal-to-noise ratio (SNR) for a single band compared with ones with less favorable conditions.
红外探测技术已在许多领域得到广泛应用。与受界面势垒高度和材料带隙限制的内光电发射和光电机制不同，对纳米厚度金属的热载流子效应的研究可能超越硅基肖特基器件探测中红外甚至远红外的能力。在这项工作中，我们研究了Cr纳米金属表面和金属/硅界面的物理特性对热载流子光学探测的影响。基于扫描电子显微镜、原子力显微镜和X射线衍射分析的结果，发现热载流子效应和光响应强度的变化高度依赖于金属表面的物理性质，如表面覆盖率、金属厚度和内应力。由于Cr和Si形成的接触层是实验中红外光探测的主要角色，金属覆盖率越高，光响应越高。此外，较厚的金属表面会使热载流子产生后转化为电流信号的时间变长，由于热载流子寿命短而导致信号退化。此外，Cr/Si结构中诱导出的具有最佳热载流子效应的薄膜能够探测高达4.2μm的红外信号。此外，与条件较差的薄膜相比，其单波段信噪比（SNR）提高了229倍。
