Analytical Model of pH sensing Characteristics of Junctionless Silicon on Insulator ISFET

In this paper, an analytical model has been developed for junctionless silicon on insulator ion-sensitive FET for pH sensing applications. The pH sensors detect the change of the hydrogen ion concentration in the aqueous solution. The modeled results show good agreement with the simulation results obtained by using Sentaurus. The electrolyte region has been considered by changing appropriate intrinsic semiconductor material in which the electron and hole charges represent the mobile ions in the aqueous solution. The effect of pH on surface potential, threshold voltage, and drain current has been investigated through model and simulations. In addition, the impact of different gate oxide materials, which act as adhesion layer, has been investigated. The pH response is defined as the amount of threshold voltage shift when the pH (in the injected solution) is varied from lower to higher values. Effect of the electrolyte region thickness on the pH sensitivity has also been discussed in this paper.