# Enhanced polarization switching characteristics of HfO2 ultrathin films via acceptor-donor co-doping

## TL;DR

This paper introduces a co-doping strategy to improve the polarization switching performance of HfO2 ultrathin films for better ferroelectric memory applications.

## Contribution

The novel approach of acceptor-donor co-doping in HfO2 films significantly enhances polarization switching characteristics and enables faster switching.

## Key findings

- La3+-Ta5+ co-doped HfO2 films show the fastest switching process reported in HfO2 polar devices.
- Co-doped films maintain robust electrical properties even at a thickness of 3 nm.
- Co-doping reduces switching barriers and improves ferroelectricity through uniform microstructure and defect control.

## Abstract

In the realm of ferroelectric memories, HfO2-based ferroelectrics stand out because of their exceptional CMOS compatibility and scalability. Nevertheless, their switchable polarization and switching speed are not on par with those of perovskite ferroelectrics. It is widely acknowledged that defects play a crucial role in stabilizing the metastable polar phase of HfO2. Simultaneously, defects also pin the domain walls and impede the switching process, ultimately rendering the sluggish switching of HfO2. Herein, we present an effective strategy involving acceptor-donor co-doping to effectively tackle this dilemma. Remarkably enhanced ferroelectricity and the fastest switching process ever reported among HfO2 polar devices are observed in La3+-Ta5+ co-doped HfO2 ultrathin films. Moreover, robust macro-electrical characteristics of co-doped films persist even at a thickness as low as 3 nm, expanding potential applications of HfO2 in ultrathin devices. Our systematic investigations further demonstrate that synergistic effects of uniform microstructure and smaller switching barrier introduced by co-doping ensure the enhanced ferroelectricity and shortened switching time. The co-doping strategy offers an effective avenue to control the defect state and improve the ferroelectric properties of HfO2 films.

Ferroelectric HfO2 is faced with an oxygen vacancy dilemma, which favors the polar phase but harm to switching behaviors. Here, the authors propose a donor-acceptor co-doping method to enhance polarization switching characteristics of the HfO2 films.