Electrical Characteristics of CNT-FETs with Symmetric Field-Effect-Free-on Source and Drain

The carbon-nanotube field-effect-transistors (CNTFETs) have been explored and proposed to be the promising candidates for the next generation integrated-circuit (IC) devices. The so-called Schottky barrier (SB)-FET is widely used to characterize the operation behavior of a CNTFET, and the Schottky barriers are affected by the gate fields at the metal-nanotube interfaces. By using the double-layered catalyst configuration (nickel and upper SiO
2
layer), SWNTs were in-situ grown across two catalytic pads on a substrate with a thinner thermal oxide layer above the channel and thicker ones at the two source/drain junction terminals. The uni-polar characteristics of a p-type CNTFET was consequently achieved by electrostatic engineering. The turn-off current (I
off
) was significantly reduced and the turn-on current (I
on
) to I
off
ratio was then increased up to ∼ 10
⁴
. The p to n conversion was observed after several cycles of measurement in a vacuum environment presumably due to removal of adsorbed O
2
molecules. On the other hand, the hysteresis behavior of transfer characteristics was still observed, suggesting that the CNTFET could be used in non-volatile memory applications.