Abstract
The implementation of dense, one-selector one-resistor (1S1R), resistive switching memory arrays, can be achieved with an appropriate selector for correct information storage and retrieval. Ovonic threshold switches (OTS) based on chalcogenide materials are a strong candidate, but their low thermal stability is one of the key factors that prevents rapid adoption by emerging resistive switching memory technologies. A previously developed map for phase change materials is expanded and improved for OTS materials. Selected materials from different areas of the map, belonging to binary Ge-Te and Si-Te systems, are explored. Several routes, including Si doping and reduction of Te amount, are used to increase the crystallization temperature. Selector devices, with areas as small as 55 × 55 nm2, were electrically assessed. Sub-threshold conduction models, based on Poole-Frenkel conduction mechanism, are applied to fresh samples in order to extract as-processed material parameters, such as trap height and density of defects, tailoring of which could be an important element for designing a suitable OTS material. Finally, a glass transition temperature estimation model is applied to Te-based materials in order to predict materials that might have the required thermal stability. A lower average number of p-electrons is correlated with a good thermal stability.
Highlights
Emerging resistive switching (RS) non-volatile memory (NVM) technologies, such as resistive random access memory (RRAM) or phase change memory (PCM), are promising candidates for the generation of advanced data storage applications[1, 2]
In order to check if the same methodology is applicable to ovonic threshold switches (OTS) materials, we compute the two bond orbital coordinates using the orbital radii reported by Chelikowsky and Phillips[37] for all Te-based OTS compositions that we could find reported in literature[27, 29, 38,39,40], and we built a similar plot
OTS materials are clustered in a small area defined by lower ionicity and higher hybridization compared to phase change materials, indicating that they are likely to form more directed covalent bonds that will lead to a slower crystallization
Summary
Emerging resistive switching (RS) non-volatile memory (NVM) technologies, such as resistive random access memory (RRAM) or phase change memory (PCM), are promising candidates for the generation of advanced data storage applications[1, 2]. A major bottleneck in the achievement of high density RRAM/PCM arrays is the lack of a high performing selector[7] device in series with each memory element that allows for accurate information storage and retrieval, by suppressing parasitic currents, through highly nonlinear current-voltage (IV) characteristics, while enabling a sufficiently high drive current for the operation of the memory element. This unique property makes chalcogenide materials convenient for selector applications[24,25,26,27,28,29]
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