  Carbon electronics based on carbon nanotube array field-effect transistors
(AFETs) and 2-dimensional graphene field-effect transistors (GFETs) have
recently attracted significant attention for potential RF applications. Here,
we explore the ultimate RF performance potential for these two unique devices
using semi-classical ballistic transport simulations. It is shown that the
intrinsic current-gain and power-gain cutoff frequencies (fT and fMAX) above 1
THz should be possible in both AFETs and GFETs. Thus, both devices could
deliver higher cut-off frequencies than traditional semiconductors such as Si
and III-V's. In the case of AFETs, we show that their RF operation is not
sensitive to the diameter variation of semiconducting tubes and the presence of
metallic tubes in the channel. The ultimate fT and fMAX values in AFETs are
observed to be higher than that in GFETs. The optimum device biasing conditions
for AFETs require smaller biasing currents, and thus, lower power dissipation
compared to GFETs. The degradation in high-frequency performance in the
presence of external parasitics is also seen to be lower in AFETs compared to
GFETs.
