Improved Tradeoff Between Subthreshold Swing and Hysteresis for MoS2 Negative-Capacitance FETs by Optimizing Gate-Stack of Hf1−x ZrxO2/Al2O3

MoS
₂
negative-capacitance field-effect transistors (NCFETs) with a gate-stack of Hf
_1-x
Zr
_x
O
₂
/Al
₂
O
₃
are fabricated, and the effects of the Zr content and the thickness of the stacked gate on electrical performance of the devices are investigated. It is found that a large improvement of device performance can be achieved by optimizing these parameters, e.g., using 6-nm Hf
_0.5
Zr
_0.5
O
₂
(Zr content of 50%) as a ferroelectric layer and 2-nm Al
₂
O
₃
as a matching layer, the relevant MoS
₂
NCFET exhibits the excellent electrical characteristics: a low subthreshold swing (
SS
) of 31.4 mV/dec, a smaller counterclockwise hysteresis of ~75 mV, and a high ON/ OFF current ratio of
$3.26\times10$
⁶
. The involved mechanisms lie in that: 1) an enhanced remnant polarization leads to low
SS
and 2) changing the thickness of the Hf
$_{1-{x}}$
Zr
_x
O
₂
and Al
₂
O
₃
can adjust the magnitude of ferroelectric capacitance and MOS capacitance to realize a reasonable match between both.