Improved Interfacial and Electrical Properties of MoS2 Transistor With High/Low-Temperature Grown Hf0.5Al0.5O as Top-Gate Dielectric

Uniform Hf
_0.5
Al
_0.5
O top-gate (TG) dielectric can be grown directly on the MoS
₂
surface using a high/low-temperature deposition method, and excellent performances for few-layer (FL) MoS
₂
transistors with Hf
_0.5
Al
_0.5
O as TG dielectric can be achieved: high mobility of 90 cm
²
/Vs, small sub-threshold swing of 77 mV/dec and low interface-state density of 1.08 × 10
¹²
eV
^-1
cm
^-2
. The involved mechanisms lie in the facts that (1) the TG dielectric can prevent the MoS
₂
surface from absorbing the oxygen and moisture in the air; (2) growing the Hf
_0.5
Al
_0.5
O dielectric at low temperature can well provide nucleation sites for its subsequent high-temperature growth; and (3) doping Al into HfO
₂
can reduce the trap charges in the resulting HfAlO dielectric to weaken the Coulomb scattering and also produce densified and uniform dielectric film. Therefore, the Hf
_0.5
Al
_0.5
O TG-dielectric structure and its growth method described in this work have a high potential to fabricate high-performance FL MoS
₂
field-effect transistors for practical electron device applications.