Drain voltage scaling in carbon nanotube transistors

Decreasing the oxide thickness in carbon nanotube field-effect transistors (CNFETs) improves the turn-on behavior. However, we demonstrate that this also requires scaling the range of the drain voltage. This scaling is needed to avoid an exponential increase in off-current with drain voltage, due to modulation of the Schottky barriers at both the source and drain contact. We illustrate this with results for bottom-gated ambipolar CNFETs with oxides of 2 and 5 nm, and give an explicit scaling rule for the drain voltage. Above the drain voltage limit, the off-current becomes large and has equal electron and hole contributions. This allows the recently reported light emission from appropriately biased CNFETs. (C) 2003 American Institute of Physics.