Band-to-Band Tunneling Leakage Current Characterization and Projection in Carbon Nanotube Transistors
Qing Lin, Carlo Gilardi, Sheng‐Kai Su, Zichen Zhang, Edward Chen, Prabhakar R. Bandaru, Andrew C. Kummel, Iuliana Radu, Subhasish Mitra, Gregory Pitner, H.‐S. Philip Wong
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 MIN ) 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 MIN 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.