Figure 2. Field-effect modulated photocurrent generation in single-gated graphene–MoS₂–graphene heterostructures.

a, Optical image of the vertical heterostructure with a multilayer MoS₂ flake (~50 nm thick) sandwiched between the Gr_T and Gr_B electrodes. b, SEM image of the same device with the Gr_T (yellow), Gr_B (red) and intermediate MoS₂ layer (blue) labelled with different false colours. c, I–V characteristics of the device under laser illumination (on white dot in b) at V_BG varying from −60 V to +60 V in steps of 20 V. Inset: variation of I_sc and V_oc with V_BG. d, Scanning photocurrent images taken at gate biases between −60 V and +60 V under a 514 nm laser (excitation power, 80 µW; spot size, 1 µm). Dashed and solid lines indicate the edges of the Gr_B and Gr_T electrodes, respectively. e–h, Schematic band diagrams of the vertical heterostructure with zero (e), negative (f), positive (g) and large positive (h) bias on the silicon back gate. Blue dots, black circles and green arrows indicate electrons, holes and photons, respectively. i, EQE of the vertical heterostructure device as a function of back-gate voltage under 80 µW, 514 nm laser excitation. Inset: EQE of the device as a function of excitation laser power at V_BG = −60 V. j, Excitation laser power-dependent EQE of another graphene-MoS₂ (16 nm)-graphene device under various excitation wavelengths at V_BG = −60 V. k, Wavelength-dependent EQE (black line with squares), absorbance (red line with circles) and IQE (blue line with triangles) of the device at V_BG = −60 V under a focused laser power of 5 µW.