Murali Krishna, Abraham Nithin, Das Sarthak, Kallatt Sangeeth, Majumdar Kausik
Department of Electrical Communication Engineering , Indian Institute of Science , Bangalore 560012 , India.
ACS Appl Mater Interfaces. 2019 Aug 21;11(33):30010-30018. doi: 10.1021/acsami.9b06835. Epub 2019 Aug 8.
Graphene, owing to its zero-band-gap electronic structure, is promising as an absorption material for ultra-wideband photodetection applications. However, graphene-absorption-based detectors inherently suffer from poor responsivity because of weak absorption and fast photocarrier recombination, limiting their viability for low-intensity light detection. Here, we use a graphene/WS/MoS vertical heterojunction to demonstrate a highly sensitive photodetector, where the graphene layer serves dual purposes, namely, as the light absorption layer and also as the carrier conduction channel, thus maintaining the broadband nature of the photodetector. A fraction of the photoelectrons in graphene encounter ultrafast interlayer transfer to a floating monolayer MoS quantum well, providing a strong quantum-confined photogating effect. The photodetector shows a responsivity of 4.4 × 10 A/W at 30 fW incident power, outperforming photodetectors reported till date where graphene is used as a light absorption material by several orders. In addition, the proposed photodetector exhibits an extremely low noise equivalent power of <4 fW/ and a fast response (∼milliseconds) with zero reminiscent photocurrent. The findings are attractive toward the demonstration of a graphene-based highly sensitive, fast, broadband photodetection technology.
由于其零带隙电子结构，石墨烯有望成为超宽带光电探测应用的吸收材料。然而，基于石墨烯吸收的探测器由于吸收较弱和光载流子复合速度快，固有地存在响应度较差的问题，限制了它们在低强度光检测中的可行性。在此，我们使用石墨烯/WS/MoS垂直异质结来展示一种高灵敏度光电探测器，其中石墨烯层具有双重作用，即作为光吸收层和载流子传导通道，从而保持了光电探测器的宽带特性。石墨烯中的一部分光电子会超快地层间转移到浮动单层MoS量子阱中，产生强烈的量子限制光闸效应。该光电探测器在30 fW的入射功率下显示出4.4×10 A/W的响应度，比迄今报道的将石墨烯用作光吸收材料的光电探测器性能高出几个数量级。此外，所提出的光电探测器表现出极低的噪声等效功率<4 fW/ ，并且具有快速响应（约毫秒级）且无光电流残留。这些发现对于展示基于石墨烯的高灵敏度、快速、宽带光电探测技术具有吸引力。
