Endurance improvement of more than five orders in Ge_xSe_1-x OTS selectors by using a novel refreshing program scheme

Selector device is critical in high-density cross-point resistive switching memory arrays for suppressing the sneak leakage current path. Ge_xSe_1-x based ovonic threshold switch (OTS) selectors have recently demonstrated strong performance with high on-state current, nonlinearity and endurance. Detailed study of its reliability is still lacking and the understanding on the responsible mechanisms is limited. In this work, for the first time, the endurance degradation mechanism of Ge-rich Ge_xSe_1-x OTS is identified. Accumulation of slow defects that remain delocalized at off-state and GeSe segregation/crystallization during cycling lead to the recoverable and non-recoverable leakage current, respectively. Most importantly, a refreshing program scheme is developed to recover and prevent the OTS degradation and the endurance can be therefore improved by more than five orders without adding additional material elements or process steps.