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.