Origin of the Ultrafast Response of the Lateral Photovoltaic Effect in Amorphous MoS₂/Si Junctions

The lateral photovoltaic (LPV) effect has attracted much attention for a long time because of its application in position-sensitive detectors (PSD). Here, we report the ultrafast response of the LPV in amorphous MoS₂/Si (a-MoS₂/Si) junctions prepared by the pulsed laser deposition (PLD) technique. Different orientations of the built-in field and the breakover voltages are observed for a-MoS₂ films deposited on p- and n-type Si wafers, resulting in the induction of positive and negative voltages in the a-MoS₂/n-Si and a-MoS₂/p-Si junctions upon laser illumination, respectively. The dependence of the LPV on the position of the illumination shows very high sensitivity (183 mV mm^-1) and good linearity. The optical relaxation time of LPV with a positive voltage was about 5.8 μs in a-MoS₂/n-Si junction, whereas the optical relaxation time of LPV with a negative voltage was about 2.1 μs in a-MoS₂/p-Si junction. Our results clearly suggested that the inversion layer at the a-MoS₂/Si interface made a good contribution to the ultrafast response of the LPV in a-MoS₂/Si junctions. The large positional sensitivity and ultrafast relaxation of LPV may promise the a-MoS₂/Si junction's applications in fast position-sensitive detectors.