A novel stack-HfO₂ top-gate structure for improving performance of network carbon nanotube transistor

Carbon nanotubes (CNTs) are regarded as a powerful contender to replace Si transistors after Moore’s law due to their advantages such as quasi-ballistic transport, high carrier mobility, and low power consumption. In the traditional CNT preparation process, CNTs are deposited on SiO₂ substrate and then the gate dielectric is deposited. In this structure, pinholes will appear between CNTs and dielectric layer, which will affect the gate-control and increase the gate leakage current. Therefore, in this paper, we designed a new stack-HfO₂ top-gate (STG) network CNTFET. By filling the pinholes between CNTs and dielectric layer, the contact interface condition is improved, reducing the subthreshold swing and improving I_on/I_off of the device. Meanwhile, through first-principles calculations, compared with the conventional structure, the interface charge transfer value of the CNT/HfO₂ interface for STG is about 5 times smaller than that of CNT/SiO₂ interface. Specifically, the mobility and SS, and I_on/I_off of the STG structure are 130 cm²/V⋅s, 156 mV/dec, and 10⁷, respectively. Taking into account the above advantages, the proposed STG structure has reference value for improving the performance of CNTFET.