Tunneling field-effect transistors (TFETs) have emerged as a potential candidate to outperform conventional metal-oxide-semiconductor FETs at low voltages, since their operation mechanism can overcome the fundamental subthreshold swing (SS) limit of 60 mV/decade at room temperature. We report carbon nanotube (CNT) based TFETs with abrupt p-i-n tunneling junctions controlled by electrostatic doping. Minimum SS (SSmin) of ∼41 mV/dec is observed with nearly no temperature dependence, as clear evidence of the TFET operation. We further investigate devices using CNTs with smaller bandgaps, reporting a record high band-to-band tunneling (BTBT) current of ∼100 nA for a single CNT. Non-linear output characteristics are observed as expected for devices operating outside of the quantum capacitance limit (QCL). Overall, electrostatically doped CNT TFETs shine a promising path for low-power electronic applications. Triple-gate CNT TFET implemented with thin gate dielectric for record high BTBT current with SSmin< 60mV/dec. Display omitted •First study of carbon nanotube TFET performance comparison for channel material with different bandgaps.•Record high band-to-band tunneling current with sub-60 mV/dec switching for carbon nanotube TFET.•Triple-gate TFET implementation utilizing thin gate dielectric to achieve high band-to-band tunneling efficiency.