Forming-Free Selectors Based on Te in an Insulating SiOx Matrix

Low voltage and low OFF-current selectors are needed to meet the requirements for cross-point array architectures in embedded memories. Chalcogenide-based selectors have been widely studied for such applications, but no single material system has yet demonstrated all the specifications required for integration with nonvolatile memory. This article presents arsenic-free selectors based on a simple and stable material system consisting of Te in an insulating SiOx matrix. By modifying the thickness and atomic composition of films, tunable switching voltage and OFF-current are achieved. Optimized forming-free SiOxTey selectors are demonstrated with a threshold voltage of ~1.2 V and an OFF-current of ~3 nA at 0.5 V. Size- and temperature-dependent measurements provide insight into the different conduction mechanisms of devices with different forming behaviors. Threshold voltage drift of ~30 mV/decade is measured for both forming-required and forming-free devices. These selectors maintain their functionality after a 300°C anneal and a recovery pulse, and they are stable after one year stored in air. Excellent endurance of 1011 cycles is reported, making these devices promising for integration with nonvolatile memory.