The recently proposed concept of graphene photodetectors offers remarkable properties such as unprecedented compactness, ultrabroadband detection, and an ultrafast response speed. However, owing to the low optical absorption of pristine monolayer graphene, the intrinsically low responsivity of graphene photodetectors significantly hinders the development of practical devices. To address this issue, numerous efforts have thus far been made to enhance the light–graphene interaction using plasmonic structures. These approaches, however, can be significantly advanced by leveraging the other critical aspect of graphene photoresponsivity enhancement—electrical junction control. It has been reported that the dominant photocarrier generation mechanism in graphene is the photothermoelectric (PTE) effect. Thus, the two energy conversion mechanisms involved in the graphene photodetection process are light-to-heat and heat-to-electricity conversions. In this work, we propose a meticulously designed device architecture to simultaneously enhance the two conversion efficiencies. Specifically, a gap plasmon structure is used to absorb a major portion of the incident light to induce localized heating, and a pair of split gates is used to produce a p-n junction in graphene to augment the PTE current generation. The gap plasmon structure and the split gates are designed to share common key components so that the proposed device architecture concurrently realizes both optical and electrical enhancements. We experimentally demonstrate the dominance of the PTE effect in graphene photocurrent generation and observe a 25-fold increase in the generated photocurrent compared to the un-enhanced cases. While further photocurrent enhancement can be achieved by applying a DC bias, the proposed device concept shows vast potential for practical applications.

最近提出的石墨烯光电探测器概念提供了卓越的特性，例如前所未有的紧凑性、超宽带检测和超快响应速度。然而，由于原始单层石墨烯的光吸收率低，石墨烯光电探测器本质上的低响应率严重阻碍了实际器件的发展。为了解决这个问题，迄今为止，人们已经做出了许多努力来利用等离子体结构来增强光与石墨烯的相互作用。然而，通过利用石墨烯光响应性增强的另一个关键方面——电结控制，可以显着推进这些方法。据报道，石墨烯中主要的光载流子产生机制是光热电（PTE）效应。因此，石墨烯光电检测过程中涉及的两种能量转换机制是光热转换和热电转换。在这项工作中，我们提出了一种精心设计的器件架构，以同时提高两种转换效率。具体来说，间隙等离激元结构用于吸收大部分入射光以引起局部加热，并且一对分裂栅极用于在石墨烯中产生pn结以增强PTE电流的产生。带隙等离子体激元结构和分裂栅极被设计为共享公共关键组件，以便所提出的器件架构同时实现光学和电学增强。我们通过实验证明了 PTE 效应在石墨烯光电流产生中的主导地位，并观察到与未增强的情况相比，产生的光电流增加了 25 倍。虽然通过施加直流偏置可以进一步增强光电流，但所提出的器件概念显示出实际应用的巨大潜力。