Fig. 4: Depolarization field-dominated photocurrent generation in the MoSSe devices.

a Schematic of the band alignment (top) and the photocarrier transfer process (both electrons and holes) in the device (bottom). The intrinsic polarization (black arrow) in the MoSSe layer induces charges in the graphene electrodes that do not fully compensate for the polarization charges. The existing depolarization field drives the photocarriers to the interface and leads to a photocurrent (gray arrow) in the direction opposite to the polarization direction. b Excitation wavelength-dependent photocurrent responsivity. This peak corresponds to the exciton resonance of MoSSe. The dots are the experimental data and the solid line is used for eye guidance. c Excitation power-dependent spontaneous photocurrent. In order to characterize the slope clearly, logarithmic coordinates are used in the figure representation. The dots are the experimental data and the dashed lines correspond to the linear and square-root fit, respectively. d Schematic of the polarization-dependent photocurrent measurement. The polarization of the incident light can be tuned by combining a linear polarizer with a \(\lambda /2\) waveplate or a \(\lambda /4\) waveplate. Linear polarization direction (e) and circular ellipticity (f) dependence of the photocurrent by varying the angle of the \(\lambda /2\) or \(\lambda /4\) waveplates, \({\theta }_{1}\) or \({\theta }_{2}\), respectively. The horizontal dashed lines are used for eye guidance.