Finite-element simulation of interfacial resistive switching by Schottky barrier height modulation

Abstract

This study demonstrates a numerical model for interfacial switching memristors based on the Schottky barrier height modulation mechanism. A resistive Schottky contact is formed for an n-type semiconductor and a high work-function metal (e.g., strontium titanate and platinum). The contact resistance is determined by the Schottky barrier height, which is influenced by the concentration of oxygen vacancies serving as space charges. Accordingly, the spatial distribution of vacancies and cell conductance can be controlled by applying a bias voltage. This interfacial switching is advantageous over filamentary switching, owing to the conductance change being more gradual in interfacial switching. In this study, a two-step numerical analysis was performed to model the conductance change in an interfacial switching memristor having a metal–oxide–metal structure of Pt/SrTiO₃/Nb-SrTiO₃, where Pt and SrTiO₃ form a Schottky contact. In the first step, the change in the spatial distribution of vacancies by an applied switching voltage was obtained by solving the drift and diffusion equations for vacancies. In the second step, after setting the Schottky barrier height according to the vacancy concentration near the contact, the cell conductance was obtained by calculating the current value by applying a small read voltage. Consequently, our simulation successfully reproduced the experimental results for the SrTiO₃-based memristor. Through this study, our device simulation for interfacial switching was successfully established, and it can be utilized in the computational design of various device architectures.