Experimental and Simulated Cycling of ISFET Electric Fields for Drift Reset

We demonstrate the cycling of electric fields within an ion-sensitive field-effect transistor (ISFET) as a method to control drift. ISFETs had a repeatable drift pattern when cycling the vertical electric field by changing the voltage between the reference electrode and the substrate. Cycling the horizontal electric field, the voltage between the drain and source of the device, showed no effect, causing the device to continue to drift as it would during normal operation. Results were confirmed with multiple pH buffer solutions. An ISFET was modeled using ATHENA. The simulation included the electrolyte modeled as a modified intrinsic semiconductor. Empirical results are confirmed with device-level simulations of an ISFET using Silvaco TCAD. The model produced a scaled current of 90 μA, which is of similar order to the experimental values of 146 μA. The repeatable drift behavior could be easily reconciled to permit the use of ISFETs for long-term continuous monitoring applications.