Enhanced resistance switching ratio of Hf0.5Zr0.5O2-based film through reducing oxygen vacancy concentration

Abstract

The resistance switching mechanism in HfO2-based resistive random access memory (RRAM) typically involves conductive filaments formed by oxygen vacancies. The inherent characteristics of this mechanism lead to low reliability and elevated off-state current in HfO2-based RRAM devices. Herein, the oxygen vacancy concentration in Hf0.5Zr0.5O2 film was decreased through the acceptor (La3+)–donor (Ta5+) co-doping strategy, which reduced off-state current from 7.6 × 10−3 A/cm2 to 3.6 × 10−6 A/cm2 at 0.5 V, increased the resistance switching ratio from 6.2 × 102 to 2.4 × 104, and improved switching stability. Following the doping of Hf0.5Zr0.5O2 film with La3+ and Ta5+, the resistance switching mechanism changes from oxygen vacancy conductive filaments to the electron capture/de-capture mechanism. The conduction mechanism of the high resistance state transitions from Schottky emission to space charge limited current, while that of the low resistance state transitions from Ohmic conduction to Fowler–Nordheim tunneling. X-ray photoelectron spectroscopy has shown that the co-doping approach decreases the concentration of oxygen vacancies, which in turn influences the alterations in the resistance switching performances and mechanisms. This study presents an effective approach for the design and improvement of HfO2-based RRAM, while also advancing the comprehension of the resistance switching mechanism influenced by doping in HfO2-based films.