Locally formed conductive filaments in an amorphous Ga2Te3 ovonic threshold switching device

Abstract

Ovonic threshold switching (OTS) selector devices based on chalcogenide materials are promising candidates for addressing the sneak current in high-density cross-point array structures owing to their high selectivity, high endurance, and fast switching speed. However, the OTS mechanism remains controversial and needs to be clarified. In this study, the formation of local conductive filaments (CFs) during threshold switching in an amorphous Ga2Te3 OTS selector device was investigated by electrical measurements and conductive-atomic force microscopy (C-AFM). The amorphous Ga2Te3 OTS selector device requires a forming process before the threshold switching processes. In addition, the off-current density (JOFF) was dependent on the area of the bottom electrode. The difference between the threshold voltage (VTH) and the hold voltage (VH) increased as the applied higher electric field increased. The drift of VTH (VTH drift) depended on the relaxation time and measurement temperature. The requirements of the forming process, area dependence of the JOFF, the difference between the VTH−VH with the applied electric field, and VTH drift are expected to depend on locally formed CFs. In addition, the analysis of the C-AFM results strongly supports the formation of local CFs during threshold switching in an amorphous Ga2Te3 OTS selector device. The understanding of OTS behavior uncovered in this study may provide guidance for improving the characteristics of and designing materials for future applications of OTS selector devices.