Improved Performance of MoS2 Negative-Capacitance Field-Effect Transistors by Optimizing Gate-Stack of Al-Doped HfO2/Al2O3

In this work, negative-capacitance field-effect transistors (NCFETs) based on Hf _{{1}-{x}} AlxOy ferroelectric films are fabricated, and the effects of the Al content in Hf _{{1}-{x}} AlxOy films and the thicknesses of the ferroelectric Hf _{{1}-{x}} AlxOy layer/Al2O3 match layer on the electrical properties of the NCFETs are focused. The results show that as the Al content decreases and the thickness of the ferroelectric layer/the match layer increases/decreases, the remanent polarization intensity of the gate-stack of Hf _{{1}-{x}} AlxOy/Al2O3 becomes large, and the subthreshold swing (SS) and total hysteresis of the relevant NCFETs are decreased. When the ratio of Al to Hf is about 1:19 to form Hf0.95Al0.05Oy ferroelectric film and the thicknesses of Hf0.95Al0.05Oy/Al2O3 are 10 nm/2 nm, respectively, excellent device performance is obtained with a low SS of 35.4 mV/dec, high ON/ OFF current ratio of 5.0\times 10^{{6}}, and negligible hysteresis of 36.2 mV. The involved mechanisms lie in enhanced ferroelectricity of Hf _{{1}-{x}} AlxOy films and a good matching between the ferroelectric capacitance and MOS capacitance of devices under the suitable structure and process parameters.