Bipolar resistive switching characteristics of a sol-gel InZnO oxide semiconductor

Abstract

This paper investigates the bipolar resistive switching characteristics of a sol-gel Ga-free InZnO (IZO) oxide semiconductor. Resistive random-access memories (RRAMs) using IZO films as the resistive switching layers are fabricated. The effects of the concentration of the IZO sol-gel solution and the thickness of the IZO layer on the RRAM performance are studied. The RRAM fabricated using a low concentration IZO solution exhibits low resistance in the high resistance state (RHRS). The resistive window is only ∼2. A higher IZO solution concentration can provide an IZO layer with a lower oxygen vacancy content. However, a substantial increase in the RHRS is not observed. The RHRS slightly increases from 350 to 500 Ω, and the resistive window is 2.7. When further increasing the thickness of the IZO resistive switching layer, an observable RHRS increase is obtained. The endurance test shows that the RHRS is 1.5 × 105 Ω and the resistive window significantly increases to 102. The composition and crystallinity of the sol-gel IZO films are analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Transmission electron microscopy (TEM) is used to examine the IZO thicknesses. The carrier conduction mechanisms and the resistive switching mechanism are also studied.