Extremely Low Leakage Threshold Switch with Enhanced Characteristics via Ag Doping on Polycrystalline ZnO Fabricated by Facile Electrochemical Deposition for an X-Point Selector

Abstract

Leakage current, that causes interferences in the read/write operation, arising from neighboring unselected or half-selected memory cells is considered as one of the main hurdles to be overcome to increase density of cross-point memory arrays. In this work, the common drawbacks for a Ag-based steep-slope threshold switching selector, threshold voltage variability, and poor cycling endurance have been mended. This is achieved by lightly doping the switching layer with Ag instead of implementing the Ag active electrode that acts as a reservoir, which provides unlimited access of Ag to the selector medium. Here, we doped polycrystalline ZnO with Ag, fabricated by facile electrochemical deposition, making a prototypical candidate for the crystalline switching layer. When the amount of Ag is limited by doping, switching characteristics, that is, threshold voltage variability and cycling endurance, are improved. Lastly, different mechanisms causing a threshold switching device to fail are also discussed for the two different test vehicles. It has been found that an unlimited Ag source causes the devices to fail in a short-circuited manner, and a limited Ag source results in devices to fail in an open-circuited manner, after repeated measurements.