Study on Device Parameters of Carbon Nanotube Field Electron Transistors to Realize Steep Subthreshold Slope of Less than 60 mV/Decade

The gate-induced band-to-band tunneling in carbon nanotube field effect transistors (CNFETs) is studied by solving the Poissson and carrier transport equations self-consistently. The transmission coefficient through the bandgap has been calculated using the Wentzel–Kramers–Brillouin (WKB) approximation. The device parameters of CNFETs with uniformly doped source/drain (S/D) regions have been investigated to find the parameter window to observe subthreshold slope (SS) of less than 60 mV/dec. It is demonstrated that the band-to-band tunneling (BTBT) current can be significantly enhanced by reducing the thickness of inter-layer oxide (t_int) between the substrate and carbon nanotube (CNT). With a thin t_int of 10 nm (SiO₂) and optimized S/D doping concentrations, a steep SS of less than 60 mV/dec can be achieved.