Unravel the Role of Atomic Layer Deposited Al ₂ O ₃ with Different Precursors on Optoelectronic Properties of IGZO Synaptic Transistors

Abstract Extending the visible light response of indium gallium zinc oxide (IGZO) phototransistors is crucial for advanced optical neuromorphic computing and artificial visual perception systems. Using water (H 2 O) as the oxidant during atomic layer deposition of aluminum oxide (Al 2 O 3 ) interlayer introduces hydroxyl impurities within IGZO, generating subgap defects that boost photo‐sensitivity (≥10 6 ) and photo‐responsivity (≥0.1 A W −1 ) under 420–620 nm visible light stimuli. The resultant IGZO/Al 2 O 3 (H 2 O) synaptic transistor successfully emulates visible‐light‐driven plasticity. In comparison, the Al 2 O 3 using ozone (O 3 ) as the oxidant is found to produce lesser defects within IGZO but creates a decent amount of negative fixed charges at the interface, improving the contact properties between IGZO and source/drain electrodes. Through innovative experimental design and in‐depth surface analysis, this work offers new insights into the microscopic origin responsible for subgap absorption and contact properties in IGZO/Al 2 O 3 structure, serving as guidelines toward designing scalable synaptic devices with enhanced optoelectronic properties.