Band-to-Band Tunneling Leakage Current Characterization and Projection in Carbon Nanotube Transistors.

Lin, Qing; Gilardi, Carlo; Su, Sheng-Kai; Zhang, Zichen; Chen, Edward; Bandaru, Prabhakar; Kummel, Andrew; Radu, Iuliana et al. · ACS Nano · 2023

basic_science · Level V

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Abstract

Carbon nanotube (CNT) transistors demonstrate high mobility but also experience off-state leakage due to the small effective mass and band gap. The lower limit of off-current (<i>I</i><sub>MIN</sub>) was measured in electrostatically doped CNT metal-oxide-semiconductor field-effect transistors (MOSFETs) across a range of band gaps (0.37 to 1.19 eV), supply voltages (0.5 to 0.7 V), and extension doping levels (0.2 to 0.8 carriers/nm). A nonequilibrium Green's function (NEGF) model confirms the dependence of <i>I</i><sub>MIN</sub> on CNT band gap, supply voltage, and extension doping level. A leakage current design space across CNT band gap, supply voltage, and extension doping is projected based on the validated NEGF model for long-channel CNT MOSFETs to identify the appropriate device design choices. The optimal extension doping and CNT band gap design choice for a target off-current density are identified by including on-current projection in the leakage current design space. An extension doping level >0.5 carrier/nm is required for optimized on-current.