Investigation on Threshold Voltage Adjustment of Threshold Switching Devices with HfO(2)/Al(2)O(3) Superlattice on Transparent ITO/Glass Substrate

Threshold voltage adjustment in threshold switching (TS) devices with HfO(2)/Al(2)O(3) superlattice (by means of changing the cycle ratio of HfO(2) to Al(2)O(3) in atomic layer deposition) is investigated to implement a transparent cross-point array. TS devices with different cycle ratios (i.e., 3:1, 3:2, and 3:3) were fabricated and studied. The threshold voltage of the devices was increased from 0.9 V to 3.2 V, as the relative contents of Al(2)O(3) layer in the superlattice were increased. At the same time, it is demonstrated that the off-resistance values of the devices were enhanced from 2.6 × 10(9) to 6 × 10(10) Ω as the atomic layer deposition (ALD) cycle ratio of HfO(2) to Al(2)O(3) layer was adjusted from 3:1 to 3:3. However, the hold voltage and the on-current values were almost identical for the three devices. These results can be understood using the larger barrier height of Al(2)O(3) layer than that of HfO(2) layer.