Ge1-xSx chalcogenide alloys for OTS applications using magnetron sputtering

Abstract

3D cross (X)-point memory arrays have attracted attention for future memory architecture due to their cost efficiency and high density. Chalcogenide-based materials are suitable candidates for 3D X-point memory because they can be stacked to form both memory and selector with a simple process. Conventional binary chalcogenide ovonic threshold switching (OTS) selectors such as GeXSe1-x or GeTe suffer from thermal instability. Furthermore, ternary OTS selectors are being investigated by doping various materials to overcome thermal instability. Here, we introduce a wide range of Ge1-xSx films to analyze and confirm the selector behavior for future applications. S-rich region (0.5 <= x <= 0.67) devices behaved as OTS selector with low leakage current (1.3 nA) and high thermal stability (amorphous up to 600 degrees C). To study the mechanism of devices with different compositions, the modified PF-model was used to calculate trap density, activation energy, subthreshold swing, and distance between traps. Additionally, extracted optical bandgap (1.65 - 3.45 eV) and urbach energy (166 - 103 meV) had good accordance with electrical characteristics of each device. This innovative research has potential to enable 3D X-point memory by combining conformal OTS selector and chalcogenide-based phase change memory.(c) 2022 Published by Elsevier B.V.