Temperature-dependent wake-up phenomena in AlScN ferrodiode memory devices

Abstract

Ferroelectric aluminum scandium nitride (AlScN) is a promising material for use in nonvolatile digital memory operating at temperatures well above the limits of current commercial technology. Ferrodiodes consisting of thin films of AlScN sandwiched between metal contacts exhibit polarization-dependent electrical conduction that can distinguish the on/off memory state with bias voltages below 10 V. However, the reliability and repeatability of key device parameters such as switching voltage and on/off ratio can change significantly with temperature. Understanding the temperature dependence of the material parameters that govern these phenomena is critical to the development of practical memory devices operating reliably at high temperature. We have systematically studied the changes in wake-up-like behavior in 40 nm AlScN films from room temperature to 700 °C. Above 300 °C, an anomalous decrease in device current arises when the applied voltage exceeds the minimum switching voltage. The temperature and rate dependence of the anomalous current loss suggests that thermally activated changes to the interlayer near the top electrode alter the local charged defect compensation. This causes the leakage current to decrease even while the net remnant polarization in the films increases.