Negative differential capacitance in ultrathin ferroelectric hafnia

Ferroelectric zirconium-doped hafnia (Hf0.5Zr0.5O2) can be used to create negative differential capacitance behaviour in capacitors and transistor gate stacks, providing reliable enhancements in switching performance. Negative differential capacitance in ferroelectrics, which can be stabilized using a dielectric, could be used to overcome the limitations of capacitive coupling in electronic devices. However, the use of negative differential capacitance in scaled silicon-based structures-such as those used in advanced low-power logic devices-remains challenging. Here we report the electrical performance enhancement due to negative differential capacitance in metal-oxide-semiconductor capacitors based on ferroelectric zirconium-doped hafnia (Hf0.5Zr0.5O2) with a thickness down to 1 nm. The devices exhibit superior performance to physically thinner control devices without the ferroelectric zirconium-doped hafnia. An S-shaped polarization-electric field relation verifies the negative differential capacitance effect. The effect is also achieved in field-effect transistors in which high-kappa hafnia is replaced with the ferroelectric zirconium-doped hafnia, leading to an increase in on current and decrease in off current along with negative drain-induced barrier lowering. The negative differential capacitance exhibits endurance over more than 10(15) cycles and can be tuned using doping that controls the interface charges.