Switching failure behaviors and doping enhanced performances of Ni/Al2O3/p+Si resistive switching devices

Device reliability is of great significance to resistive switching applications, and reset failure dominates the deterioration of cycling endurance. Although it has been found that the excessive aggregation of movable ions could lead to the reset failure, the quantitative studies on the defect movement have seldom been conducted. Hence, the Ni/Al2O3/p(+)Si sandwiched structure is fabricated by magnetron sputtering, and the reset failure phenomenon is analyzed. The measurements on the resistive switching behaviors demonstrate that the space-charge-limited current mechanism is responsible for the electroforming process, while the current conduction in subsequent switching cycles obeys the hopping mechanism. Temperature-dependent I-V measurements reveal that the resistance states are closely related with both the hopping distance (R) and hopping energy barrier (W) between adjacent localized states. Short hopping distance of 0.66 +/- 0.02nm and low hopping activation energy of 1.72 +/- 0.06meV will lead to the unrecoverable breakdown of Al2O3 dielectric layer, large leakage current, and deteriorative memory window. 1.9at.% ZnO doped into Al2O3 dielectric layer can lower the switching voltages and the compliance current of the devices, which will alleviate the aggregation of the localized states during the cycling process. As a result, the R and W values in high resistance state are stabilized at 2.24 +/- 0.04nm and 5.76 +/- 0.11meV during 100 direct current switching cycles, and the memory window is significantly improved. A physical model is proposed to understand the reset failure mechanism of Ni/Al2O3/p(+)Si devices.