Switching mechanisms of CMOS-compatible ECRAM transistors—Electrolyte charging and ion plating

Abstract

To elucidate the internal chemical physics of measured CMOS-compatible electrochemical random-access memory (ECRAM) devices, we constructed a 2D semiconductor device simulation, including ions and electrochemical reactions, and used it to fit measured devices. We present the results of a device simulation model that includes Cu+ ions’ diffusion and the charge transfer reaction between the WOx conduction band electron and Cu+ (i.e., “Cu plating”). Reproducing the linear response of ECRAM devices, the effect of charging HfOx by the Cu+ ions is sufficient, and WOx is not being doped by the Cu+ ions. While potentiation is supported by the formation of an electron channel, an efficient depression requires the formation of high positive charge density at the channel material. At higher Cu+ flux, Cu+ reaches and penetrates the WOx layer. While this effect enhances the potentiation response, it also initiates the “plating” reactions. Including this reaction is essential to reproducing the data of devices exhibiting sub-linear responses. We suggest that electron trapping by ions (i.e., plating) would constitute a long-term degradation process even for H+ based devices.