Figure 2. Experimental demonstration of a VO₂-based hyper-FET.

(a) Schematic of a hyper-FET consisting of a two-terminal VO₂ device (=4 μm; =2 μm) in series with the channel of a conventional Si n-MOSFET (L_g=100 μm; W=100 μm). V_VO2 is the voltage across the VO₂ device and V_GS′ is the effective gate-to-source voltage across the MOSFET. (b) I_DS–V_GS transfer characteristics of the hyper-FET exhibiting abrupt and reversible modulation of the channel current I_DS as a function of the gate-source voltage V_GS. The abrupt turn-ON and turn-OFF of the hyper-FET corresponds to the IMT and MIT in VO₂, respectively. (c) Switching slope (S) as a function of I_DS revealing the steep-slope characteristics (S<60 mV per decade) of the hyper-FET during the forward and reverse gate bias sweep. (d) Output characteristics (I_DS–V_DS) of the hyper-FET with excellent current saturation. (e) Current versus voltage characteristics of the VO₂ device with (red) and without (blue) the MOSFET in series, illustrating the electrically triggered abrupt IMT. The channel resistance of the MOSFET acts as a series resistor, modifying the current–voltage dynamics through a feedback and inducing a negative differential resistance NDR (red) across the phase transition in VO₂. The NDR reduces the voltage across the VO₂ by ΔV_NDR. The current has been normalized to the width of the Si n-MOSFET to show that the abrupt IMT in VO₂ triggers the abrupt turn-ON of the hyper-FET shown in b.