Fig. 3. Device 2.

a DC drain-source current as a function of the gate voltage; the measurements were made with the device illuminated at 2 THz $\left(V_{ds}=-0.1\mathrm{V}\right)$. Inset: Absolute value of the rectified current as a function of the gate voltage (no drain-source bias voltage). The direction of the current flow changes at zero values of the current. b Extracted ν_pl values for τ between 25 fs and 60 fs. Red dots depict ν_pl for τ = 40 fs. The inset compares the extracted values of ν_pl fo τ = 40 fs with the theoretical predictions (cf. Figure 2d)