Analytical modeling of a high-K underlap dielectric- and charge-modulated silicon-on-nothing FET-based biosensor

Abstract

Field-effect transistor (FET)-based biosensors with stacked gate oxides provide low leakage current and high sensitivity. However, an undesirable interfacial layer of silicate and silicon dioxide is formed in between the stacked oxides. In this paper, an underlap silicon-on-nothing FET-based biosensor with high-K gate oxide is presented for the detection of charged biomolecules, thereby removing the unwanted interfacial layer while preserving the sensitivity of the device. The study is based on a surface potential model for the proposed device, which is developed from Poisson’s equation by incorporating the dielectric and charge properties of the biomolecules. A threshold voltage model is then developed to examine the sensitivity of the device. The change in the device characteristics upon the accumulation of biomolecules is investigated to understand the impact of the biomolecules on the behavior and sensitivity of the device. The results show that the proposed device is highly sensitive to charged biomolecules, and that the charge of the biomolecules is more important than their dielectric properties for modulating the device characteristics. The results indicate that the proposed device has potential to be chosen as a new type of highly sensitive, nanosize, label-free biosensor with no unwanted interfacial layer. The analytical model is validated against two-dimensional (2-D) numerical simulation data obtained from ATLAS (SILVACO).