Ge content compromise to the performance optimization of GexAsySez OTS materials for selector applications

Abstract

Germanium is a critical dopant in ovonic threshold switching (OTS) selectors, yet how its concentration influences the performance and failure mechanisms of Ge–As–Se-based OTS materials remains poorly understood. In this study, Ge–As–Se OTS devices with varying Ge concentrations are fabricated and characterized. Increasing the Ge content is found to reduce the threshold voltage, albeit at the expense of prolonged switching time and increased voltage drift. The leakage current initially decreases with higher Ge content but subsequently rises due to the formation of conductive Ge–Ge bonds. Microstructural analysis of the devices after 109 cycles reveals that void formation and interlayer diffusion are the key failure mechanisms. An optimal Ge content window of 28%–44% is identified, which balances low leakage current, high endurance, and acceptable switching speed. These findings elucidate the role of Ge doping and provide a theoretical foundation for the design of novel high-performance OTS materials.