Modified Schottky Barrier CNTFET with lightly doped drain

Abstract

For the first time, a modified Schottky barrier carbon nanotube field-effect transistor (SB-CNTFET) with lightly doped drain (LDD) has been proposed. The newly designed CNTFET benefits from the advantages of both SB in source and the lightly doped ohmic drain contact. Simulations are based on two-dimensional non-equilibrium Green's function solved self-consistently with Poisson's equation. To get to an improved electrical characteristic, comparisons have been made among four CNTFET structures which are conventional SB-CNTFETs, triple LDD-CNTFET (TLDD-CNTFET), double LDD-CNTFET and Schottky source and ohmic drain CNTFET. The results show that the TLDD-CNTFET design decreases the leakage current significantly and increases on–off-current ratio as well as the cut-off frequency. It is also demonstrated that TLDD-CNTFET structure possesses three perceivable steps in the potential profile of the channel, which leads to additional lateral electric field peaks inside the channel and thus improve the immunity against short-channel effects. The important parameters such as transconductance, on–off ratio, subthreshold swing, cut-off frequency, delay and drain-induced barrier lowering of the CNTFETs have been calculated and discussed. Results show that by using lightly doped regions in the drain of SB-CNTFETs, the dc and ac characteristics have been considerably improved compared with the conventional SB-CNTFET.