An Aqueous Route to Oxygen-Deficient Wake-Up-Free La-Doped HfO<sub>2</sub> Ferroelectrics for Negative Capacitance Field Effect Transistors
Pavan Pujar, Haewon Cho, Young‐Hoon Kim, Young‐Hoon Kim, Nicolò Zagni, Jeonghyeon Oh, Eunha Lee, Srinivas Gandla, Pavan Nukala, Young‐Min Kim, Young‐Min Kim, Muhammad A. Alam, Sunkook Kim
Abstract
The crucial role of nanocrystalline morphology in stabilizing the ferroelectric orthorhombic (o)-phase in doped-hafnia films is achieved via chemical solution deposition (CSD) by intentionally retaining carbonaceous impurities to inhibit grain growth. However, in the present study, large-grained (>100 nm) La-doped HfO 2 (HLO) films are grown directly on silicon by adopting engineered water-diluted precursors with a minimum carbonaceous load and excellent shelf life. The o-phase stabilization is accomplished through a well-distributed La dopant, which generates uniformly populated oxygen vacancies, eliminating the need for oxygen-scavenging electrodes. These oxygen-deficient HLOs show a maximum remnant polarization of 37.6 μC/cm 2 (2 P r ) without wake-up and withstand large fields (>6.2 MV/cm). Furthermore, CSD-HLO in series with Al 2 O 3 improves switching of MOSFETs (with an amorphous oxide channel) based on the negative capacitance effect. Thus, uniformly distributed oxygen vacancies serve as a standalone factor in stabilizing the o-phase, enabling efficient wake-up-free ferroelectricity without the need for nanostructuring, capping stresses, or oxygen-reactive electrodes.