Comparison of resistive switching characteristics using copper and aluminum electrodes on GeO(x)/W cross-point memories

Comparison of resistive switching memory characteristics using copper (Cu) and aluminum (Al) electrodes on GeO(x)/W cross-points has been reported under low current compliances (CCs) of 1 nA to 50 μA. The cross-point memory devices are observed by high-resolution transmission electron microscopy (HRTEM). Improved memory characteristics are observed for the Cu/GeO(x)/W structures as compared to the Al/GeO(x)/W cross-points owing to AlO(x) formation at the Al/GeO(x) interface. The RESET current increases with the increase of the CCs varying from 1 nA to 50 μA for the Cu electrode devices, while the RESET current is high (>1 mA) and independent of CCs varying from 1 nA to 500 μA for the Al electrode devices. An extra formation voltage is needed for the Al/GeO(x)/W devices, while a low operation voltage of ±2 V is needed for the Cu/GeO(x)/W cross-point devices. Repeatable bipolar resistive switching characteristics of the Cu/GeO(x)/W cross-point memory devices are observed with CC varying from 1 nA to 50 μA, and unipolar resistive switching is observed with CC >100 μA. High resistance ratios of 10(2) to 10(4) for the bipolar mode (CCs of 1 nA to 50 μA) and approximately 10(8) for the unipolar mode are obtained for the Cu/GeO(x)/W cross-points. In addition, repeatable switching cycles and data retention of 10(3) s are observed under a low current of 1 nA for future low-power, high-density, nonvolatile, nanoscale memory applications.