Defect-Engineered PECVD-Grown hBN Enabling Effective Charge Trapping in IGZO Synaptic Transistors

Neuromorphic devices require reliable charge trapping mechanisms to emulate synaptic functionalities such as hysteresis, memory retention, and weight modulation; however, conventional oxide semiconductor-based devices often suffer from limited stability due to the absence of well-defined trapping layers. Here, we demonstrate that defect-engineered hexagonal boron nitride (hBN) grown by plasma-enhanced chemical vapor deposition (PECVD) can serve as an effective charge-trapping interlayer in indium-gallium-zinc oxide (IGZO) synaptic transistors. The PECVD-grown hBN exhibits significant structural disorder, oxygen-related bonding, increased Urbach energy, and reduced film density, indicating the presence of abundant defect-induced localized states that provide energetically favorable sites for charge trapping and retention. When the hBN film is integrated with the IGZO semiconducting channel layer, it significantly enhances the charge trapping efficiency, resulting in a pronounced increase in the hysteresis window from 0.8 to 4.7 V, along with improved synaptic characteristics such as enhanced potentiation/depression behavior and stable long-term memory retention. These results highlight the potential of PECVD-grown defect-rich hBN as a functional charge-trapping layer for high-performance oxide semiconductor-based neuromorphic devices.