Channel-length scaling for effects of single defects in carbon nanotube transistors

We investigate channel-length scaling characteristics for effects of a single charged defect in a carbon nanotube field-effect transistor (CNFET), using the nonequilibrium Greens function method. We find that the threshold voltage shift due to a single charge in midchannel increases with the decreasing channel length. In a p-type CNFET, the relative current reduction in the on-state due to a positive charge and the relative current change in the turn-on region due to a negative charge increase apparently with the decreasing channel length. The threshold voltage shift and relative current change caused by a single charge for short channel CNFETs increases with the gate-oxide thickness much faster than that for long channel CNFETs. For a short channel p-type CNFET, the current reduction in the on-state due to a positive charge may be larger than 60% and the threshold voltage shift due to a negative charge may amount to 0.6 V.