Tunable Performances in OTS Selectors Thanks to Ge₃Se₇-As₂Te₃

ALD Heterojunction Ovonic Threshold Switches

“…The subsequent 2 cycles show stable switching at 2.5 V, by definition the threshold voltage V TH . This finding is consistent with PVD OTSs with similar composition and thickness . A 100 μA current compliance was set to protect the device from undesirable high currents.…”

“…25,26 Particularly, we posed our attention on Ge-Se-As-Te compositions. 21 Unfortunately no OTS chalcogenide composition including arsenic has ever been realized using ALD. The transition from PVD-to ALD-OTS enables the realization of new device architectures able to exploit in full the potential of 3D cross-point architectures.…”

“…This finding is consistent with PVD OTSs with similar composition and thickness. 21 A 100 μA current compliance was set to protect the device from undesirable high currents. A common figure of merit that can be extracted from the DC-IV plot is the leakage current, I leak , defined as the current at half V TH .…”

“…35 It has been reported that the threshold voltage in OTS devices has a strong dependency on the frequency of operation, or equivalently, on the delay occurring between pulses. This phenomenon, often referred to as threshold voltage drift, 21,36,37 is extremely important as it determines a window of operating conditions for the selector in an actual memory array. In Figure 3d, we report the value of V TH as a function of the delay between the applied voltage pulses.…”

“…Previously, only binary ALD OTS films have been developed, , while the use of chalcogenide alloys comprising three or more elements is crucial for OTS performance even in PVD films. Such compositions are needed to address simultaneously a number of problems such as a suitable bandgap limiting the OTS subthreshold current , and electrical and thermal stability to guarantee device reliability. , The introduction of Arsenic into chalcogenide glasses, particularly, generated a breakthrough as this element was found to improve the thermal stability of the film and avoid crystallization; , incorporation of this element into OTS devices resulted in extremely stable selectors with high endurance. , Particularly, we posed our attention on Ge-Se-As-Te compositions . Unfortunately no OTS chalcogenide composition including arsenic has ever been realized using ALD.…”