Scalability of Sulfur-Based Ovonic Threshold Selectors for 3D Stackable Memory Applications

A two-terminal selector is an essential element for high-density 3D stackable memory arrays. Suppressing sneak current, the device also needs to provide extremely high current density to melt-quench the storage layer in phase-change memory (PCM). Recently, an ovonic threshold switching (OTS) selector based on amorphous GeS demonstrated a large current density, which seems to be promising for 3D stackable PCM application. Herein, the scalability of GeS OTS selectors is investigated as the device scales down from 200 to 60 nm. Interestingly, the ON/OFF current, threshold voltage, and switching speed hardly change as the device scales down, whereas the ON current density exponentially grows. A large current density, ≈35.4 MA cm⁻², is achieved in 60 nm-sized devices. The high current density endows the GeS selector with great potential for use in high-density 3D stackable memory applications.