Interplay between transient interfacial photocurrent and surface nonlinear photocurrent in graphene/MoS2 heterostructure

Electron transfer across heterostructure interfaces plays a pivotal role in the functionality of modern electronic and optoelectronic devices, such as photocatalysts, solar cells, and phototransistors. However, interaction with ultrafast lasers could trigger a nonlinear optical response within individual materials to compete with the interfacial photocurrent in the heterostructure. Distinguishing the interplay between interfacial photocurrent and surface nonlinear photocurrent is challenging yet interesting. Herein, terahertz (THz) emission spectroscopy is employed to demonstrate the synergistic interaction between interfacial charge transfer and nonlinear photocurrent (photogalvanic effect in MoS₂ and photon drag effect in graphene), thereby enhancing THz radiation in the graphene/MoS₂ heterostructure compared with pure MoS₂ and graphene. Interestingly, the contribution of interlayer charge transfer to the THz radiation gradually increases as the pump fluence increasing from 0.14 mJ/cm² to 1.70 mJ/cm². Our work offers an effective way to actively control the interface effect of heterostructures, potentially leading to advances in the utilization of graphene-based heterostructures in photonics and electronics devices.