Bandgap Extraction at 10 K to Enable Leakage Control in Carbon Nanotube MOSFETs

Carbon nanotube (CNT) transistors exemplify the fundamental tradeoff between desirable high mobility and undesirable leakage current due to the small effective mass and bandgap. To understand leakage current limits in high-speed CNT transistors, electrical bandgaps are extracted on 12 single-CNT top-gate MOSFETs from the energy gap between thermionic emission and band-to-band tunneling (BTBT) at 10 K. At 300 K the minimum I
_OFF
at 0.5 V V
_DS
is analyzed as a function of bandgap between 0.96 eV and 0.43 eV with I
_OFF-MIN
from 0.2 pA/CNT to 15 nA/CNT. NEGF simulation validates the bandgap extraction methodology and reproduces the experimental MOSFET I
_OFF-MIN
data. A TCAD model calibrated to this work’s leakage data projects the accessible I
_ON
-I
_OFF
design space bounded by CNT bandgap, indicating E
_G
> 0.65 eV (d
_CNT
< 1.3 nm) is needed to achieve 100 nA/
$\mu \text{m}$
at 0.5 V V
_DD
and 250 CNT/
$\mu \text{m}$
for channel length above 20 nm. An E
_G
of 1.06 eV (d
_CNT
= 0.8 nm) can deliver
$2750\times $
tunable range of I
_OFF
by adjusting V
_T
, which exceeds the
$400\times $
tunable range of I
_OFF
used in Si CMOS platform technologies.