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/ HfO x 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/HfO x /Ni device resulted from the Schottky barrier of defect states in the SiO x /HfO x 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/HfO x /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.