The transfer of charge carriers across the optically excited hetero-interface of graphene and semiconducting transition metal dichalcogenides (TMDCs) is the key to convert light to electricity, although the intermediate steps from the creation of excitons in TMDC to the collection of free carriers in the graphene layer are not fully understood. Here, we investigate photo-induced charge transport across graphene–MoS2 and graphene–WSe2 hetero-interfaces using time-dependent photoresistance relaxation with varying temperature, wavelength, and gate voltage. In both types of heterostructures, we observe an unprecedented resonance in the inter-layer charge transfer rate as the Fermi energy (EF) of the graphene layer is tuned externally with a global back gate. We attribute this to a resonant quantum tunneling from the excitonic state of the TMDC to EF of the graphene layer and outline a new method to estimate the excitonic binding energies (Eb) in the TMDCs, which are found to be 400 meV and 460 meV in MoS2 and WSe2 layers, respectively. The gate tunability of the inter-layer charge transfer timescales may allow precise engineering and readout of the optically excited electronic states at graphene–TMDC interfaces.

中文翻译：

---

光激发石墨烯-TMDC界面层间电荷传输共振的观察

电荷载流子在石墨烯和半导体过渡金属二硫属化物 (TMDC) 的光激发异质界面上的转移是将光转化为电的关键，尽管从 TMDC 中激子的产生到在 TMDC 中收集自由载流子的中间步骤石墨烯层尚未完全了解。在这里，我们使用随温度、波长和栅极电压变化的时间相关光阻弛豫来研究跨越石墨烯-MoS2 和石墨烯-WSe2 异质界面的光致电荷传输。在这两种类型的异质结构中，我们观察到层间电荷转移率出现前所未有的共振，因为石墨烯层的费米能量 (EF) 通过全局背栅进行外部调整。我们将其归因于从 TMDC 的激子态到石墨烯层的 EF 的共振量子隧穿，并概述了一种估计 TMDC 中激子结合能 (Eb) 的新方法，发现它们分别为 400 meV 和 460 meV。分别为 MoS2 和 WSe2 层。层间电荷转移时间尺度的栅极可调性可以允许精确设计和读出石墨烯-TMDC 界面处的光激发电子态。