Characteristics Extraction of Fully Symmetric GAA and Top-Gate CNTFETs with 6 nm Channel Length

Abstract

High-compatible applications for top-gate and gate-all-around (GAA) carbon nanotube field-effect transistors (CNTFETs) are presented. The geometrical specifications of these CNTFETs are evaluated and their effects on the characteristics are highlighted. The channel length is considered 6 nm, while the drain, source, and spacer are symmetric with channel length. The evaluations are performed by the COMSOL Multiphysics, and the Shockley-Read-Hall (SRH) recombination model is used to analyze doping, electron, and hole distributions. The drain and source wells are considered with donor doping of ND0 = 1 × 1021 cm−3 and acceptor doping of NA = 1 × 1019 cm−3, then, the current-voltage (I–V) characteristics are extracted. Also, the CNTs with 1.12 nm are placed accurately through the channel, and the terminals are constructed with graphene. The I–V curves show that the threshold voltage for the top-gate and GAA are 0.23 V and 0.21 V, respectively. Besides, the short channel effect (SCE) is reduced which is confirmed by a subthreshold swing (SS) of 62 mV/dec for the top-gate and 58 mV/dec for the GAA. Moreover, drain-induced barrier lowering (DIBL) and ION/IOFF ratio parameters are studied to investigate scaled-down devices. The discussed structures are compared by the figure of merit (FoM) of ΔVDIBLSS/(ION/IOFF), which shows more desirable and better channel control. The temperature variations show that there is no dramatic increase in the leakage current, which proves that symmetric structure is reliable in short-channel devices.