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

Uniform Hf0.5Al0.5O top-gate (TG) dielectric can be grown directly on the MoS2 surface using a high/low-temperature deposition method, and excellent performances for few-layer (FL) MoS2 transistors with Hf0.5Al0.5O as TG dielectric can be achieved: high mobility of 90 cm2/Vs, small sub-threshold swing of 77 mV/dec and low interface-state density of $1.08\times {10}^{{12}}$ eV−1cm−2. The involved mechanisms lie in the facts that (1) the TG dielectric can prevent the MoS2 surface from absorbing the oxygen and moisture in the air; (2) growing the Hf0.5Al0.5O dielectric at low temperature can well provide nucleation sites for its subsequent high-temperature growth; and (3) doping Al into HfO2 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 Hf0.5Al0.5O TG-dielectric structure and its growth method described in this work have a high potential to fabricate high-performance FL MoS2 field-effect transistors for practical electron device applications.