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/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.