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

For a given three different Si doping concentrations at room and high temperatures, the threshold voltage shift (ΔV_th) on silicon-doped hafnium-oxide-based ferroelectric field effect transistor (FeFET) is experimentally investigated. It turned out that charge trapping in the gate stack of FeFET (versus polarization switching in the gate stack of FeFET) adversely affects ΔV_th. Charge trapping causes the positive ΔV_th, while polarization switching causes the negative ΔV_th. The dominance of polarization switching is predominantly determined by the total remnant polarization (2P_r), which can be controlled by adjusting Si doping concentration in the hafnium-oxide layer. As the Si doping concentration increases from 2.5% to 3.6%, and 5.0%, 2P_rdecreases 19.8μC cm^-2to 15.25μC cm^-2, and 12.5μC cm^-2, which leads to ΔV_thof -0.8 V, -0.09 V, and +0.1 V, respectively, at room temperature. At high temperature, the effect of polarization switching is degraded due to the decreasedP_r, while the effect of charge trapping is very independent of temperature. For those three different Si doping concentrations (i.e. 2.5%, 3.6%, and 5.0%), at the high temperature, ΔV_thof FeFET is -0.675 V, -0.075 V, and +0.15 V, respectively. This experimental work should provide an insight for designing FeFET for memory and logic applications.