Realization of Selector-Memory Bi-Functionality with Self-Current Regulation Utilizing Poly-Crystalline Based GST Electrolyte for Memristor Hardware Development

Abstract

Conductive bridge random-access memory (CBRAM) are two terminal devices that offer excellent switching performance. In addition, CBRAM shows various switching modes, including volatile threshold switching (TS) and nonvolatile threshold switching (N-TS). These properties expand its applications to memory, selector, biological synapses, and neurons. However, due to the uncontrollable behavior of stochastic switching between TS and N-TS in CBRAM devices, a novel approach is needed to improve the switching performance of CBRAM. Moreover, conventional devices that have different stacking between TS and N-TS increase fabrication cost and worsen the device yield. Here, the selector-memory bi-functionality with self-current regulation effect of Ag-inserted Ge2Sb2Te5 (GST) thin films is demonstrated. Selector-memory bi-functionality, having TS behavior with an adjustable on/off current, with confined conductive filaments (CFs) improves the uniformity and reduces the fabrication cost by implementing TS/N-TS in a single stack. From the material analysis, it becomes evident that confined Ag-based CFs within GST films are key factors for realizing selector-memory bi-functionality. The selector-memory bi-functionality is achieved through the reaction of Ag metal cations with non-bonded Te atoms in GST film depending on field polarity. These results suggest that the Ag-inserted GST film contributes to the development of large-scale nonvolatile memory and neuromorphic application. The study demonstrates a completely new design of CBRAM devices that exhibit uniform switching and reliable selector-memory bi-functionality. An Ag-inserted structure between poly-crystalline Ge2Sb2Te5 thin films is revealed to restrict Ag-based CF formation with adjustable selector-memory bi-functionality. Poly-crystalline Ge2Sb2Te5 thin film permits adjustable multilevel resistance states with selector property, stable retention, and good endurance.image