Two-dimensional materials without lattice constraints can be combined into form heterojunctions via van der Waals forces, providing opportunities for the future development of novel high-performance photodetectors. In non-vertical heterojunction devices with long carrier transport channels, SRH recombination due to defect and interface states in the heterojunction and Langevin recombination due to Coulomb interactions induce large amounts of photogenerated carrier recombination, leading to low quantum efficiencies of the heterojunction. At the same time, defect and interface trap states, as well as the long channel of the non-vertical heterojunction device, lead to a slow response speed of the device. In this work, a 2D WSe2/MoTe2 vertical heterojunction photodiode with a transparent graphene top electrode has been designed to simultaneously achieve high sensitivity and fast response speed of photodetectors. Benefiting from the vertical device structure, high-quality interface and low contact resistance, the photogenerated electron-hole pairs can be efficiently separated and transported. The photodiode exhibits remarkable rectification characteristics with a rectification ratio as high as 1.4 × 104, and provides a broadband and self-powered photodetection from the visible to NIR bands (405–1064 nm) with a maximum responsivity of 0.33 A/W at 785 nm. In particular, the photodiode achieves an ultra-fast rise/fall time of 6.49/6.22 μs at 0 V and a further reduction of the response time to 1.68/1.2 μs at a reverse bias of −1 V. This ultra-fast response allows the photodiode to detect switching signals with a cutoff frequency of more than 70 kHz and 200 kHz at 0 V and −1 V, respectively. This work opens up new opportunities for the development of integrated 2D photodetectors with low power consumption, high sensitivity, and high speed.

中文翻译：

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用于具有超快响应和高灵敏度的自供电光电二极管的二维 Gr/WSe2/MoTe2 垂直异质结


没有晶格约束的二维材料可以通过范德华力组合成异质结，为未来新型高性能光电探测器的发展提供了机会。在具有长载流子传输通道的非垂直异质结器件中，由于异质结中的缺陷和界面态引起的SRH复合以及由于库仑相互作用引起的朗之万复合引起大量的光生载流子复合，导致异质结的量子效率较低。同时，缺陷和界面陷阱态以及非垂直异质结器件的长沟道导致器件响应速度慢。在这项工作中，设计了具有透明石墨烯顶电极的2D WSe2/MoTe2垂直异质结光电二极管，以同时实现光电探测器的高灵敏度和快速响应速度。得益于垂直器件结构、高质量界面和低接触电阻，光生电子-空穴对可以有效分离和传输。该光电二极管具有出色的整流特性，整流比高达 1.4 × 104，可提供从可见光到近红外波段 (405–1064 nm) 的宽带自供电光电检测，在 785 nm 处的最大响应率为 0.33 A/W 。特别是，光电二极管在 0 V 时实现了 6.49/6.22 μs 的超快上升/下降时间，并在 -1 V 反向偏压下将响应时间进一步缩短至 1.68/1.2 μs。这种超快响应允许光电二极管检测0V和-1V时截止频率分别超过70kHz和200kHz的开关信号。 这项工作为开发低功耗、高灵敏度、高速度的集成二维光电探测器开辟了新的机遇。