Improving the GeAsSe Ovonic Threshold Switching Characteristics by Carbon Buffer Layers for Ultralow Leakage Current (0.4 nA) and Low Drift Characteristics

VolatileOvonic threshold switching (OTS) selectors havebeen regardedas the critical component of highly integrated three-dimensional (3D)cross-point array nonvolatile memory systems. However, relativelyhigh leakage current hinders the further reduction of power consumptionin the crossbar array. In addition, the threshold voltage drift phenomenonhinders the improvement of device reliability. Utilizing the bufferlayer can effectively reduce the interaction between electrodes andthe active layer in the cross-point architecture. Here, it manifeststhat leakage current can be reduced to similar to 0.4 nA with a 5 nmthick amorphous carbon layer as a buffer layer in the GeAsSe-basedOTS device, where the carbon layer stabilizes the composition of GeAsSeduring the electrical switching cycles. It is also found that thecarbon layer leads to a lower threshold voltage drift (35.6 mv/dec)and excellent endurance (>10(9) cycles with similar to 0.4nAON-state current). The conduction mechanism analysis demonstratesthat the inhibition of the carbon layer on drift originates from thehigh barrier height from delocalized states transformed into localizedstates. This work clearly demonstrates the role of the carbon layerand facilitates future 3D crossbar-storage technology applications.