Ultralow Voltage Resistive Switching in Hafnium–Zirconium Oxide

Abstract

Ultralow SET and RESET voltage are essential for high-density, low-power, and small heat dissipation nonvolatile random-access memory (NVRAM) elements. A nanoscale polycrystalline Hf_0.75Zr_0.25O₂ (HZO) thin films on Pt/Si substrate are fabricated and investigated for suitability for bipolar resistive switching. The device illustrates monoclinic and tetragonal/orthorhombic phases with weak ferroelectricity and robust resistive switching. Small remanent polarization (≈0.1 μC cm⁻²) may assist in the height reduction of barrier height and ease the electron for transport. Remarkably, the Al/HZO/Pt/Si device, consisting of thin films with 10 and 5 nm thicknesses, exhibits a switching voltage below −30 mV from a low-resistance state (LRS) to a high-resistance state (HRS). It shows a significant R_OFF/R_ON ratio of 10⁶, making it suitable for low power consumption and minimal heat dissipation devices. Moreover, the utilization of an ultrathin film (5 nm) results in an improved reduction (< 0.7 V) of the operating window at the positive voltage.  Direct tunneling and the Fowler–Nordheim tunneling model are performed in current–voltage (I–V) data to study the charge transportation behavior over a trapezoidal and triangular potential barrier. These results of the HZO candidate may stimulate the futuristic nonvolatile resistive random-access memory (ReRAM) in the optoelectronic industry.