Optimization of Subthreshold Swing and Hysteresis in Hf0.5Zr0.5O2-Based MoS2 Negative Capacitance Field-Effect Transistors by Modulating Capacitance Matching.

Abstract

Negative capacitance field effect transistors made of Hf0.5Zr0.5O2 (HZO) are one of the most promising candidates for low-power-density devices because of the extremely steep subthreshold swing and high open-state currents resulting from the addition of ferroelectric materials in the gate dielectric layer. In this paper, HZO thin films were prepared by magnetron sputtering combined with rapid thermal annealing. Their ferroelectric properties were adjusted by changing the annealing temperature and the thickness of HZO. Two-dimensional MoS2 back-gate negative capacitance field-effect transistors (NCFETs) based on HZO were prepared as well. Different annealing temperatures, thicknesses of HZO thin films, and Al2O3 thicknesses were studied to achieve optimal capacitance matching, aiming to reduce both the subthreshold swing of the transistor and the hysteresis of the NCFET. The NCFET exhibits a minimum subthreshold swing as low as 27.9 mV/decade, negligible hysteresis (∼20 mV), and the ION/IOFF of up to 1.58 × 107. Moreover, a negative drain-induced barrier lowering effect and a negative differential resistance effect have been observed. This steep-slope transistor is compatible with standard CMOS manufacturing processes and attractive for 2D logic and sensor applications as well as future energy-efficient nanoelectronic devices with scaled power supplies.