Experimental study of threshold voltage shift for Si:HfO₂based ferroelectric field effect transistor

Area of Science:

• Materials Science
• Electrical Engineering
• Solid State Physics

Background:

• Ferroelectric field-effect transistors (FeFETs) are promising for memory and logic applications.
• Understanding threshold voltage shifts (ΔVth) is crucial for FeFET performance.
• Silicon doping in hafnium oxide impacts FeFET characteristics.

Purpose of the Study:

• To experimentally investigate the threshold voltage shift (ΔVth) in silicon-doped hafnium-oxide-based FeFETs.
• To analyze the influence of Si doping concentration and temperature on ΔVth.
• To elucidate the competing effects of polarization switching and charge trapping on ΔVth.

Main Methods:

• Fabrication of FeFETs with varying Si doping concentrations in the hafnium oxide layer.
• Experimental measurement of threshold voltage shift (ΔVth) at room and high temperatures.
• Analysis of the relationship between Si doping, remnant polarization (2Pr), and ΔVth.

Main Results:

• Charge trapping leads to a positive ΔVth, while polarization switching results in a negative ΔVth.
• Increasing Si doping concentration from 2.5% to 5.0% decreased remnant polarization (2Pr) from 19.8 μC cm⁻² to 12.5 μC cm⁻².
• At room temperature, ΔVth shifted from -0.8 V to +0.1 V with increasing Si doping. At high temperatures, ΔVth ranged from -0.675 V to +0.15 V, with polarization switching effects diminishing.

Conclusions:

• Si doping concentration in hafnium oxide is a key parameter to control the trade-off between polarization switching and charge trapping in FeFETs.
• The study provides insights into optimizing FeFET design for specific memory and logic applications by managing ΔVth.
• Temperature significantly affects polarization switching, while charge trapping remains relatively temperature-independent.