An experimental study on the fringe field effect of VDS on ISFET pH sensors

Abstract In the operation of an ISFET, there is a question whether the drain-to-source voltage, VDS, might produce a non-uniform distribution of electric field across the electrolyte—insulator—semiconductor interfaces and thus affect the results of pH measurements. In this paper calculations show that the double-layer field is an order of magnitude higher than the insulator field at any point along the channel direction of the ISFET. An experiment was designed such that VDS can be set at various values to examine the effect of VDS on pH measurements. It is shown that with a gate length of 10 μm at VDS ⩽ 3 V, the effect of VDS on ISFET pH sensors is not observable.