Sensitivity Enhancement of Dual Gate Field-Effect Transistors Using Stacked Bottom Gate Dielectrics

Dual gate field-effect transistors (DGISFETs) have prompted interest because of the sensitivities higher than the Nernst limit through capacitive coupling. The bottom gate (BG)–semiconductor interface plays a crucial role in the sensitivity enhancement. Stacked gate dielectrics are utilized for the improved performance of the metal–oxide–semiconductors and the thin-film transistors while the utilization of stacked dielectrics is limited to DGISFETs. The use of a stacked BG dielectric for the sensitivity enhancement of DGISFETs is the impetus of the current work. Four DGISFETs were used for elucidation of the significance of the BG dielectric–semiconductor interface on the sensitivity of DGISFETs. The influence of the material properties on the sensitivity of the DGISFETs was studied with the help of X-ray photoelectron spectroscopy depth profiling and atomic force microscopy. The pH sensitivities of two DGISFETs were compared with two different BG dielectrics (silicon dioxide and the stack of yttrium oxide/silicon dioxide) and yttrium oxide as TG dielectric. For further confirmation, DGISFETs with tantalum pentoxide as the TG dielectric with the same set of BG dielectrics were studied. The experimentally obtained pH sensitivities were validated through the simulation results. A highlight of this study is elucidation of the role of the BG dielectric–semiconductor interface on the performance of the DGISFETs. Sensitivity values of 847 and 796 mV/pH were obtained with yttrium oxide and tantalum pentoxide as the TG dielectrics, respectively.