Understanding Switching Mechanism of Selector-Only Memory Using Se-Based Ovonic Threshold Switch Device

In this study, we investigated the effect of material composition on the selector-only memory (SOM) characteristics of ovonic threshold switch (OTS) device. By controlling the selenium (Se) concentration within the chalcogenide film, we were able to optimize the electrical properties. OTS devices co-sputtered with Se exhibited excellent characteristics, including a sufficient memory window (MW > 1.2 V) and fast operation speed ( similar to 10 ns). Furthermore, we found that the desired MW could be obtained by varying the pulse height during the write process. The optical bandgap and bond nature of chalcogenide film were analyzed by UV-vis and Raman spectroscopy, revealing that the Se is the key element to the SOM operation of the OTS device. To understand the correlation between electrical properties and modification of the bond topology, we employed density functional theory (DFT) calculations. Finally, we explained the mechanism of SOM operation by introducing a thermally assisted hopping (TAH) model and analyzing the trap behavior in OTS devices. From our experimental results, we have demonstrated that the stability of delocalized traps formed depending on the polarity of the write pulse plays a crucial role in the operation of the SOM device. Our findings provide valuable insights into the complex relationship between material composition and the electrical characteristics of SOM devices.