Electron transport across ultrathin ferroelectric Hf0.5Zr0.5O2 films on Si

Abstract

In this work, we report on the electron transport properties of ultrathin (~2.5nm) ferroelectric polycrystalline Hf0.5Zr0.5O2 (HZO) films grown by the Atomic Layer Deposition (ALD) technique directly on the highly doped Si substrate. On the devices with TiN top electrode we demonstrate the reversible electroresistance change R↑/R↓ up to 3 across HZO layer following the polarization reversal. We further correlate the electroresistance switching with the polycrystalline structure of the the HZO layer, the polarization measurements, the current lateral distribution over the HZO layer as well as DFT calculations of the electronic band structure. Such analysis reveals that the polarization switching in ferroelectric HZO grains contribute to the current transport in TiN/HZO/n+-(p+-)Si devices.