Analysis of independent gate operation in Si nano tube FET and threshold prediction model using 3D numerical simulation

Abstract

In this paper, silicon nanotube field effect transistors (SiNT-FETs) are investigated for independent gate operation using 3D numerical simulation. The parameters, $$\mathrm{I_{ON} , I_{OFF}, V_{T}}$$ION,IOFF,VT, and the unity gain cut-off frequency $$\mathrm{(f_{T}}$$(fT) are studied in the independent-gate mode. The SiNT-FET we have considered has two gates, namely outer and inner gates, and can be simultaneously driven or independently driven. The physical gate oxide thicknesses of the outer and inner gates of the device are to be converted into effective gate oxide thicknesses due to the non-Euclidean geometry associated with the tube structure. The effective gate oxide thicknesses are different for the same outer and inner physical gate oxide thickness. Since the inner and outer gates are asymmetric, the device parameters extracted at the outer and inner gates are different. Since the independent gate operation allows dynamic threshold voltage adjustment, a model to predict the threshold voltage also known as the threshold voltage sensitivity model is developed for the SiNT device by modifying the double gate FinFET model. These models are verified by TCAD simulation results to validate their accuracy.