Realization of Enhanced Long‐Term Visual Memory for Indium–Gallium–Zinc Oxide‐Based Optical Synaptic Transistor

Abstract Amorphous indium–gallium–zinc oxide (IGZO)‐based optical synaptic transistor using visible light as the signal that shows a clear difference between long‐term memory (LTM) and short‐term memory (STM) is introduced in this study. However, since oxide semiconductors, including IGZO, do not sense visible light due to their high band gap energy of around 3.0 eV, defects are generated intentionally within IGZO channel layer to enable sensitivity to the visible light by inserting two layers of mesh‐structured titanium dioxide (m‐TiO 2 ) inside the channel layer. Additionally, a layer of thin film‐structured hafnium dioxide (HfO 2 ) is inserted inside the channel to increase the persistent photoconductivity (PPC) effect. This increased PPC effect causes the device to maintain the current long after the light signal is removed. Therefore, the average difference between LTM and STM is achieved ≈110 times, showing a clear difference between LTM and STM. Additionally, 721% of maximum paired‐pulse facilitation (PPF) is achieved. Thus, the device introduced in this study is believed to lead the coming technology such as interactive appliances including displays and robots.