Self-Selection Unipolar $\hbox {HfO}_{x}$ -Based RRAM

In this paper, we study the effect of highly doped n⁺/p⁺ Si as the bottom electrode on unipolar RRAM with Ni-electrode/ HfOx structure. With heavily doped p⁺-Si as the bottom electrode, RRAM devices illustrate the coexistence of the bipolar and the unipolar resistive switching. Meanwhile, by substituting heavily doped n⁺ -Si, the switching behavior changes to that of the self-rectifying unipolar device. The asymmetry and rectifying reproducible behavior in a n⁺-Si/HfOx/Ni device resulted from the Schottky barrier of defect states in the SiOx/HfOx junction and n⁺ Si substrate, but this behavior is not seen for the p⁺-Si bottom electrode case. With rectifying characteristics and high forward current density observed in the Ni/HfOx/n⁺Si device, the sneak current path in the conventional crossbar architecture was significantly suppressed. We believe that the proposed structure is a promising candidate for future crossbar-type RRAM applications.