Figure 4. Field-effect modulated photocurrent generation in a single-gated graphene–MoS₂–metal heterostructure.

a, Schematic three-dimensional illustration of the device layout. b, Schematic illustration of the side view of the device, with a multilayer MoS₂ flake sandwiched between a Gr_B electrode and a top metal electrode (Ti). The device was fabricated on transparent ITO on a glass substrate (as the back gate) with 30-nm-thick Al₂O₃ as the gate dielectric to allow illumination to transmit through the back side of the substrate to reach the graphene–MoS₂ contact. c, Optical image of a graphene–MoS₂–metal heterostructure device. d,e, Schematic band diagrams of the graphene–MoS₂–metal heterostructure at negative and positive back-gate voltages, respectively. f, Scanning photocurrent images taken at V_BG = −1, 0 and +1 V (80µW, 514 nm excitation, with a spot size of 1 µm). Dashed and solid lines indicate the edges of the Gr_B and top metal electrodes, respectively. g, I–V characteristics of the device under laser illumination (on red dot in c) with V_BG varying from −1 V to 1 V in steps of 0.5 V. The I–V curve obtained in the dark at V_BG = −1 V passes through the origin, indicating that gate leakage is negligible. h, Excitation laser power-dependent EQE under various excitation wavelengths at V_BG = −1 V. i, Wavelength-dependent EQE at a laser power of 5 µW.