Fast operation of a WO3-based solid-state electrochromic transistor

Electrochromic transistors (ECTs) have attracted attention as advanced memory technology because one can use both electrochromism and switching of electrical conductivity in a nonvolatile manner. Although several solid-state ECTs have been proposed so far, their operating speed is still slow (operating time >1 min) as compared to liquid-based ECTs (∼20 s) due to their asymmetric gate-source electrode configuration. Here we demonstrate a fast operation of a solid-state ECT. We fabricated a solid-state ECT with three terminal gate-source-drain electrodes using an amorphous WO3 film as the electrochromic material and amorphous TaOx as the solid electrolyte. By the insertion of a thin ZnO layer between the source and drain electrodes to achieve pseudo symmetric gate-source electrode configuration, we greatly reduced the operation time to less than 1 s at ±3 V application while keeping the on-to-off ratio of ∼30. The present approach is effective to improve the operating speed of ECTs and may be practically used in advanced memory technologies.