Self-Selection Unipolar HfOₓ -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/ HfOxstructure. 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/HfOxjunction 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.