  The so-called Boltzmann Tyranny defines the fundamental thermionic limit of
the subthreshold slope (SS) of a metal-oxide-semiconductor field-effect
transistor (MOSFET) at 60 mV/dec at room temperature and, therefore, precludes
the lowering of the supply voltage and the overall power consumption. Adding a
ferroelectric negative capacitor to the gate stack of a MOSFET may offer a
promising solution to bypassing this fundamental barrier. Meanwhile,
two-dimensional (2D) semiconductors, such as atomically thin transition metal
dichalcogenides (TMDs) due to their low dielectric constant, and ease of
integration in a junctionless transistor topology, offer enhanced electrostatic
control of the channel. Here, we combine these two advantages and demonstrate
for the first time a molybdenum disulfide (MoS2) 2D steep slope transistor with
a ferroelectric hafnium zirconium oxide layer (HZO) in the gate dielectric
stack. This device exhibits excellent performance in both on- and off-states,
with maximum drain current of 510 {\mu}A/{\mu}m, sub-thermionic subthreshold
slope and is essentially hysteresis-free. Negative differential resistance
(NDR) was observed at room temperature in the MoS2 negative capacitance
field-effect-transistors (NC-FETs) as the result of negative capacitance due to
the negative drain-induced-barrier-lowering (DIBL). High on-current induced
self-heating effect was also observed and studied.
