光学微带天线-石墨烯复合结构红外光探测器的研究

Graphene has received substantial attention as an appealing material for infrared photodetection due to its unique photonic and optoelectronic properties. However, as a critical drawback, the low absorption of graphene due to the atomic layer thickness restricts photoresponse to a low level. In this project, we propose to integrate optical microstrip antennas with graphene infrared photodetectors for an enhancement in photoresponse. The project is conducted through electromagnetic simulation, fabrication, optical spectrum measurement, and opto-electronic characterization. There are four scientific problems to investigate: 1) the compatibility between the optical microstrip antenna and the graphene field effect transistor structure, 2) the impact of graphene on the resonance behaviors of the antenna, 3) the dependence of the photoresponse enhancement on the resonant coupling property of the antenna and the tuning mechanism of the photoresponse enhancement, 4) the influence of the antenna distribution on the photoresponse under even illumination and zero source-drain bias. Based on the investigation, we propose to realize the prototype devices, clarify the resonance behaviors of the antenna integrated with graphene, reveal the dependence of the photoresoponse enhancement on the resonant coupling efficiency between the propagating incident light and the local field, figure out the tuning mechanism of the resonant coupling efficiency and thus the photoresoponse enhancement, obtain a high-performance optical coupling structure, and achieve high photoresponse and low dark current in the graphene infrared photodetector integrated with an optical microstrip antenna. This project will experimentally and theoretically benefit the development of high-performance graphene infrared photodetectors.

石墨烯独特的光电性质已经引起红外光探测领域国际上的关注，石墨烯原子层厚度的光吸收是制约红外探测器响应率的关键问题。本项目提出利用光学微带天线增强石墨烯红外光探测器响应率的研究，通过对光学微带天线-石墨烯复合结构的电磁仿真、制备加工、光谱测量、光电测量等手段，研究1）光学微带天线与石墨烯场效应管结构的兼容，2）石墨烯对于光学微带天线共振行为的影响，3）石墨烯光响应的增幅与光学微带天线共振耦合特性的依赖关系及调控机制、4）光学微带天线的分布对于均匀光照射且源漏零偏置情况下光响应的影响等四个科学问题，实现原型器件，弄清光学微带天线-石墨烯复合结构的共振机理，探索行波-局域场耦合效率的调制规律，揭示行波-局域场耦合效率的优化对于大幅增强石墨烯光响应的作用，获得高性能微纳光耦合结构，实现光学微带天线-石墨烯复合结构的高响应率和低暗电流，为高性能石墨烯红外光探测器的发展提供实验和理论依据。

本项目针对石墨烯在高性能红外探测领域的重要应用前景与其光吸收率过低的深刻矛盾，提出利用光学微带天线增强石墨烯红外光探测器响应率的研究。构建了石墨烯表面电导率的物理模型，实现了光学微带天线-石墨烯复合结构的电磁仿真。发展了人工微纳结构集成的石墨烯器件的制备工艺，成功实现了光学微带天线-石墨烯复合结构红外光探测原型器件。通过对比实验与仿真，揭示了微带天线大幅提高石墨烯光吸收和光响应的物理原理。在此基础上对器件结构进行了优化，使光吸收率逼近100%，石墨烯的光响应率提高1到2个量级。利用各向异性光学微带天线的高偏振选择性，使石墨烯红外光响应的偏振消光比达到30:1，高出之前报道的所有单种二维材料（包括与光子结构集成的二维材料）偏振探测消光比3-10倍，同时提升石墨烯响应率70倍。通过光学微带天线的非对称集成，使金属-石墨烯-金属光探测结构在泛光照射下具有自驱动光响应，并且比一般光栅集成石墨烯的响应率高出1个数量级以上，为开发源漏零偏置的低暗电流高响应率的高性能探测模式打下了科学基础。进而把基于局域场操控增强亚波长材料光耦合的原理推广到其它微纳光耦合结构，突破了亚波长介质光耦合弱以及光耦合结构自身损耗严重的难题，利用金属修饰结构显著增强了低折射率纳米颗粒的共振散射，实现了基于光学方法的8nm精细尺寸分辨，超越了相同放大倍率的SEM观测以及动态光散射表征（最常用的纳米颗粒尺寸表征方法）的精度和效率，推动了低折射率纳米颗粒尺寸和折射率精细且高效表征技术的发展；提高等离激元微腔集成的量子阱长波红外吸收至82%，抑制光耦合结构吸收损耗至18%；获得100nm以下的超窄线宽和3倍的探测波段拓展；对高性能量子阱红外焦平面的发展有重要意义。在Phys. Rev. Lett.、Adv. Opt. Mater.、Nanoscale等国际权威刊物上发表SCI论文6篇；申请专利3项，1项获得授权，2项进入实质审查。