Improved Interfacial and Electrical Properties of MoS₂ Transistor with High/Low-Temperature Grown Hf_0.5Al_0.5O as Top-Gate Dielectric

Uniform Hf_0.5Al_0.5O 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 Hf_0.5Al_0.5O 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 1.08×10¹² 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 Hf_0.5Al_0.5O 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 Hf_0.5Al_0.5O 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.