Effect of gate capacitance ratio on ion-sensitive FET memory

Abstract

This paper introduces the ISFET Memory device, which combines nonvolatile memory capabilities with the traditional ISFET functionality for pH sensing applications. The device's performance is evaluated in both writing and erasing modes, with particular emphasis on how adjusting the gate capacitance ratio (GCR) influences the operating voltages and sensitivity. Results show that optimizing the GCR to 0.43 significantly reduces the voltages required for writing and erasing operations, while also enhancing sensitivity across a broader pH range. The device achieves maximum sensitivities of 1609 mV/pH in the writing state and 940 mV/pH in the erasing state, far exceeding the ideal ISFET sensitivity of 58.2 mV/pH. Furthermore, the device demonstrates adaptability to different pH ranges: the writing mode is better suited for pH values from 2 to 10, whereas the erasing mode is more effective for the remaining pH range.