Fig. (3) shows a close up of Fig. (2) from the VDS range of 1.8 V to 3.0V. Plotted on Python from data collected on the LabVIEW V.I.  The resulting curves are not evenly spaced.  The spacing between lines increases as the gate voltage increases.  The duration of the experiement focuses on the I/V portion  before breakdown occurs.   The current increases linearly until about 5 volts then becomes asymptotic approaching the peak current.