Improved Interfacial and Electrical Properties of MoS 2 Transistor With High/Low-Temperature Grown Hf 0.5 Al 0.5 O 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 $1.08\times {10}^{{12}}$ 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.