Internal Electrical Noises of BioFET Sensors Based on Various Architectures

The results of a comparative literature analysis of internal electrical noises and signal-to-noise ratio for nanoscale BioFET (biological field-effect transistor) and DNA (deoxyribonucleic acid) sensors based on different architectures MIS (metal-insulator-semiconductor), EIS (electrolyte-insulator-semi-conductor) and ISFET (ion-selective field-effect transistor) are presented. Main types, models and mechanisms of internal noises of bio- & chemical field-effect based sensors are analyzed, summarized and presented. For the first time, corresponding detail electrical equivalent circuits were built to calculate the spectral densities of noises generated in the active part of a solid (semiconductor, dielectric) and in an aqueous solution for MIS, EIS and ISFET structures based sensors. Complete expressions are obtained for the rms (root mean square) value of the noise current (or voltage), as well as the noise spectral densities for the architectures under study. The miniaturization of biosensors leads to a decrease in the level of the useful signal-current. For successful operation of the sensor, it is necessary to ensure a high value of the SNR (signal-to-noise ratio). In case of weak useful signals, it is necessary to reduce the level of internal electrical noise. This work is devoted to a detailed study of the types and mechanisms of internal electrical noises in specific biosensor architectures.