Fig. 1. (a) Schematic diagram of the MoSe2/graphene photodetector, (b) optical image of the heterostructure device, (c) Raman mapping, (d) Raman spectrum of the graphene and MoSe2/graphene heterostructure, (e) AFM morphology of the MoSe2/graphene heterostructure, and (f) thickness of graphene and MoSe2. Scale bar, 5  μm.

Fig. 2. Output curves at various input light: (a) Vg=0  V and (b) Vg=80  V. (c) Transfer curves at light off and on, Vds=1  V. (d) Photocurrent varying with gate voltage under various light power. Incident light, 550 nm.

Fig. 3. (a) KPFM image of graphene/MoSe2 heterostructure; scale bar, 5  μm. (b) Surface potential between graphene and MoSe2. (c) Band diagram of graphene and MoSe2 before contact under dark. After they are in contact, the Fermi level is aligned, and the band bending of MoSe2 in the area adjacent to graphene decreases slightly. Band diagram of graphene and MoSe2 under light illumination, (d) Vg < VDirac and (e) Vg > VDirac. Blue dashed lines represent the Fermi level.

Fig. 4. (a) Responsivity of the graphene/MoSe₂ heterostructure photodetector varying with the wavelength from 450 to 1000 nm. (b) Responsivity varying with light power, and the curve can be fitted by the equation R∼Pβ−1. Blue dots represent experimental data, and the red dashed line is the fitting curve: Vds=1  V, Vg=0  V.

Fig. 5. Time-dependent photocurrent of the graphene/MoSe2 heterostructure device, and the time constant τ is about 22 s.