Self-Consistent Electrostatic Framework for Quantum and Geometric Capacitance Analysis in CNTFETs Under Structural Variations

초록

Carbon nanotube field-effect transistors (CNTFETs) are among the most promising candidates for post-silicon device technologies, yet a quantitative understanding of how structural and compositional variations govern gate-dependent electrostatics remains lacking. In this work, we present a charge-based, self-consistent capacitance decomposition framework that integrates chirality-dependent quantum mechanical density of states with classical finite element method (FEM) electrostatics, systematically separating the total gate capacitance into the quantum capacitance Cq, geometric capacitance Cgeo, and electrode parasitic capacitance Cpar. Using this framework, we investigate how CNT chirality, metallic tube fraction in random networks, and array pitch each reshape the bias-dependent balance between Cq- and Cgeo-limited regimes and quantify their impact on saturation current and switching delay. Our results provide a physically intuitive interpretation of capacitance limiting mechanisms and offer practical design guidelines for chirality engineering, purity control, and pitch optimization in next-generation CNTFET technologies. © 2013 IEEE.

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