Optimal stoichiometry and performance evolution in As-Se based OTS devices

Abstract

Arsenic-selenium (As-Se)-based ovonic threshold switching (OTS) devices are essential components for facilitating effective non-volatile memory systems. This study examines the performance evolution of As-Se OTS devices with different arsenic concentrations. A non-monotonic pattern is evident in device performance: the leakage current initially diminishes and subsequently escalates with rising As content, whereas the threshold voltage displays an inverse tendency. The gadget containing 50 % As exhibits reduced leakage and enhanced durability features. Molecular dynamics simulations indicate that at low arsenic level, Se-Se homopolar bonds are predominant; however, these bonds are markedly diminished at intermediate compositions. At elevated arsenic concentrations, arsenic-selenium heteropolar bonds diminish, but arsenic-arsenic interactions prevail. Analysis of the coordination number reveals that the average coordination number, at 50 % arsenic, nearly attains the optimal threshold of 2.4, signifying enhanced network stiffness. Furthermore, electronic structure study indicates that the bandgap reaches its peak at a 50 % composition, reflecting substantial contributions from both As and Se p-orbitals. These findings determine the ideal As-Se stoichiometry for high-performance OTS devices and provide significant insights for material and device design.