Fig. 4: TCAD simulations.

a TCAD simulations calibrated against experimental transfer curve at pH = 7 in the reverse-sweep direction for the WSe2(top)/MoS2(bottom) ISFET. The inset shows simulation results for pH values ranging between 5 and 9. b Drain current vs fluid-gate voltage characteristics at different pH values, extracted using TCAD simulations. c Simulated magnitude of the electric field across the WSe2 channel v/s gate voltage (for VFG and VBG when the other is set to 0 V). d Simulated electric field contours with applied VFG and VBG (arrows indicate the field direction). e Simulated density of channel (WSe2) charge v/s gate voltage (for VFG and VBG when the other is set to 0 V).