Ferroelectric-Antiferroelectric Transition of Hf_1–xZr_xO₂ on Indium Arsenide with Enhanced Ferroelectric Characteristics for Hf_0.2Zr_0.8O₂

Abstract

The ferroelectric (FE)−antiferroelectric (AFE) transition in Hf 1−x Zr x O 2 (HZO) is for the first time shown in a metal−ferroelectric−semiconductor (MFS) stack based on the III-V material InAs. As InAs displays excellent electron mobility and a narrow band gap, the integration of ferroelectric thin films for nonvolatile operations is highly relevant for future electronic devices and motivates further research on ferroelectric integration. When increasing the Zr fraction x from 0.5 to 1, the stack permittivity increases as expected, and the transition from FE to AFE-like behavior is observed by polarization and current−voltage characteristics. At x = 0.8 the polarization of the InAsbased stacks shows a larger FE-contribution as a more open hysteresis compared to both literature and reference metal−ferroelectric−metal (MFM) devices. By field-cycling the devices, the switching domains are studied as a function of the cycle number, showing that the difference in FE−AFE contributions for MFM and MFS devices is stable over switching and not an effect of wake-up. The FE contribution of the switching can be accessed by successively lowering the bias voltage in a proposed pulse train. The possibility of enhanced nonvolatility in Zr-rich HZO is relevant for device stacks that would benefit from an increase in permittivity and a lower operating voltage. Additionally, an interfacial layer (IL) is introduced between the HZO film and the InAs substrate. The interfacial quality is investigated as frequency-dependent capacitive dispersion, showing little change for varying ZrO 2 concentrations and with or without included IL. This suggests material processing that is independently limiting the interfacial quality. Improved endurance of the InAs-Hf 1−x Zr x O 2 devices with x = 0.8 was also observed compared to x = 0.5, with further improvement with the additional IL for Zr-rich HZO on InAs.

Ultrathin Al2O3 interfacial layer for Hf0.5Zr0.5O2-based ferroelectric field-effect transistors

“…In the pristine state, the remanent polarization values of both HZO/silicate and HZO/Al 2 O 3 samples were nearly identical (11-12 µC cm −2 ). The two samples exhibited slightly different coercive fields, probably because of the different built-in potentials of HZO and Si resulting from the different ILs [17]. Because the difference between the positive and negative coercive fields represents the two threshold voltage (V th ) values associated with the two polarization states in FeFETs [18], the MW of the FeFETs containing HZO/Al 2 O 3 is anticipated to be wider than that of FeFETs including HZO/silicate.…”

Ferroelectricity in Epitaxial Tetragonal ZrO2 Thin Films

“…[41] This second approach is the most commonly adopted in the literature. [15,27,[42][43][44] In this study, we demonstrate the ferroelectricity of t-phase ZrO 2 thin films with varying thicknesses ranging from 7 to 42 nm. First, the t-phase of ZrO 2 is evidenced by X-ray Diffraction (XRD).…”

Optimization of ferroelectricity and endurance of hafnium zirconium oxide thin films by controlling element inhomogeneity

“…In this study, we implemented a design strategy involving the inhomogeneous distribution of Hf/Zr elements in (Hf,Zr)O2 thin films to optimize their endurance while minimizing antiferroelectric-like wake-up effects. Leveraging the distinct phase structure characteristics and electrical properties of HfO2, Hf-rich Hf0.8Zr0.2O2, Hf0.5Zr0.5O2, Zr-rich Hf0.2Zr0.8O2 and ZrO2 [39,40], we designed and fabricated both homogeneous and inhomogeneous element distribution for (Hf,Zr)O2 thin films with a 1:1 ratio of Hf : Zr, as illustrated in Fig. 1(a).…”