Fig. 4: Ultrafast photocurrent dependence on electric field.

a, b The ultrafast photocurrent and corresponding normalized photocurrent under 300 K. c, d The ultrafast photocurrent and corresponding normalized photocurrent under 180 K. The insets are the extracted decay times in regions II and III. Note that the oscillations are a result of impedance mismatch, which slightly varies with devices and do not correspond to an internal physical process.