Quasi-ballistic carbon nanotube array transistors with current density exceeding Si and GaAs

Abstract

Nearly ballistic carbon nanotube array transistors are realized with current densities outmatching conventional semiconductors.

Gigahertz integrated circuits based on carbon nanotube films

“…1d). Previously reported CNT FETs with submicrometre channels also exhibited good on-state performance 9,11,13 , but the subthreshold swing was usually larger than 300 mV dec . Therefore, our CNT FETs provide a significant improvement on both on-state and off-state performance when compared with other CNT film FETs (Fig.…”

“…It should be emphasized that the fabrication method developed and device structure optimization made in this work are not limited to any specific material system (for example, random network). CNT material systems can be further improved by such methods as aligning CNTs into high-density arrays 9,11,13 , reducing the defect density of CNTs in films (using, for example, direct chemical-vapour-deposition-grown CNTs), and using single-chirality CNTs with different diameters for different applications (with different requirements, for example, high-performance applications with large-diameter CNTs and low-power applications using small-diameter CNTs with a larger bandgap). The methods developed in this work can be readily used, when better material systems become available, to construct large-scale ICs with a performance exceeding that of Si CMOS ICs.…”

“…Prototype device studies using individual CNTs have shown that nanotube electronics have the potential to outperform Si CMOS technology in both performance and power consumption [3][4][5][6] , and are even close to the theoretical limits for all field-effect-transistor(FET)-based binary switches 7,8 . Recently, FETs were fabricated using aligned CNT arrays, and shown to have a higher channel conductance (at a lower bias) than that of Si CMOS FETs 9 . However, the key performance metrics reported for such CNT FETs, including on-state current density (I on ) and transconductance (g m ), are still substantially lower than those of conventional Si CMOS FETs at the same characteristic length [9][10][11][12][13] .…”

“…Recently, FETs were fabricated using aligned CNT arrays, and shown to have a higher channel conductance (at a lower bias) than that of Si CMOS FETs 9 . However, the key performance metrics reported for such CNT FETs, including on-state current density (I on ) and transconductance (g m ), are still substantially lower than those of conventional Si CMOS FETs at the same characteristic length [9][10][11][12][13] . The ideal material system for high-performance CNT electronics has been identified as a parallel array film of intrinsic pure semiconductor single-walled nanotubes of a single chirality with a diameter of approximately 1.3 nm and no defects, and a tube-tube spacing of 5-8 nm (ref.…”

“…Although such an ideal material system is yet to be realized, many breakthroughs in the purification and controlled synthesis of CNTs have been made in recent years [15][16][17][18][19] , suggesting the possibility of achieving the required nanotube purity and array density before 2020 14 . Using randomly oriented or aligned CNT array films, various types of CNT thin-film FETs have been fabricated [9][10][11][12][13] . However, hindered by the limited performance of nanotube FETs, the operation speed of CNT integrated circuits (ICs) [20][21][22][23][24][25][26][27][28][29][30][31] typically falls short of their expected terahertz potential, and that achieved by Si CMOS circuits (gigahertz), by several orders of magnitude.…”