Improvement on the electron transport efficiency of the carbon nanotube field effect transistor device by introducing heterogeneous-dual-metal-gate structure

To improve the carbon nanotube field effect transistor (CNTFET) device performance and enhance the electron transport efficiency of the device, a heterogeneous-dual-metal-gate (HDMG)-CNTFET is proposed. By appropriately modifying the transport model for single-metal-gate (SMG)-CNTFET, the electron transport properties of the HDMG-CNTFET device are investigated. The results indicate that the work function WGS of the metal gate near the source (S-gate) is fixed such that it is equal to that of the intrinsic CNT, and the work function WGd of the metal gate near the drain (D-gate) is selected to be smaller than WGS within a certain range, the electric field distribution can be optimised and the average electron velocity in the CNTFET channel can be significantly increased; at the same time, due to the electric potential modulation by the D-gate, the device has a lower threshold voltage. When the same operating voltage is applied, HDMG-CNTFET has a larger on-state current than SMG-CNTFT; and due to the shielding effect of the drain voltage variation by D-gate, the HDMG-CNTFET device exhibits good gate-control ability and can suppress the drain-induced barrier lower effect, hot electron effect and ambipolar conduction behavior compared with SMG-CNTFET. This study, by reasonably selecting the gate electrode work function of the HDMG-CNTFET, can effectively overcome the deficiency of existing research on improving the CNTFET performance at the expense of reducing the on-current, more importantly, can improve the electron transport efficiency, thereby improving the characteristic frequency and reducing the delay time of the device, which will be of benefit to CNTFET application in high-speed/high-frequency circuit.