Investigation of light doping and hetero gate dielectric carbon nanotube tunneling field-effect transistor for improved device and circuit-level performance

We perform a comparative study (both for device and circuit simulations) of three carbon nanotube tunneling field-effect transistor (CNT-TFET) designs: high-K gate dielectric TFETs (HK-TFETs), hetero gate dielectric TFETs (HTFETs) and a novel CNT-TFET-based combination of light doping and hetero gate dielectric TFETs (LD-HTFETs). At device level, the effects of channel and gate dielectric engineering on the switching and high-frequency characteristics for CNT-TFET have been theoretically investigated using a quantum kinetic model. This model is based on two-dimensional non-equilibrium Green's functions solved self-consistently with Poisson's equations. It is revealed that the proposed LD-HTFET structure can significantly reduce leakage current, enhance control ability of the gate on the channel, improve the switching speed, and is more suitable for use in low-power, high-frequency circuits. At circuit level, using HSPICE with look-up table-based Verilog-A models, the performance and reliability of CNT-TFET logic gate circuits is evaluated on the basis of power consumption, average delay, stability, energy consumption and power-delay product (PDP). Simulation results indicate that, compared to a traditional CNT-TFET-based circuit, the one based on LD-HTFET has a significantly better performance (static noise margin, energy, delay, PDP). It is also observed that our proposed design exhibits better robustness under different operational conditions by considering power supply voltage and temperature variations. Our results may be useful for designing and optimizing CNTFET devices and circuits.