Enhanced Optoelectronic Synaptic Performance in Sol-Gel Derived Al-Doped ZnO Thin Film Devices

Area of Science:

• Materials Science
• Neuroscience
• Optoelectronics

Background:

• Oxide-based materials are crucial for developing advanced neuromorphic devices.
• Sol-gel methods offer a scalable route for fabricating functional thin films.
• Optoelectronic synapses require precise control over material properties for optimal performance.

Purpose of the Study:

• To fabricate and characterize Al-doped ZnO (AZO) optoelectronic synaptic devices.
• To investigate the impact of varying Al concentrations on the structural, optical, and synaptic properties of ZnO films.
• To demonstrate the potential of AZO for in-sensor computing and neuromorphic vision systems.

Main Methods:

• Sol-gel fabrication of AZO thin films with Al concentrations ranging from 0 to 4.0 wt%.
• Structural and optical characterization using techniques like X-ray diffraction and photoluminescence spectroscopy.
• Evaluation of synaptic device performance, including learning-forgetting dynamics, persistent photoconductivity (PPC), and long-term memory (LTM) simulations.

Main Results:

• Moderate Al doping (2.0 wt%) optimized the ZnO bandgap (3.31 eV), crystal orientation, and defect levels.
• The 2.0 wt% AZO device demonstrated superior synaptic performance with the lowest forgetting rate and longest memory retention.
• Al-oxygen vacancy complexes were identified as key contributors to enhanced carrier lifetime and memory characteristics.
• Visual memory simulations confirmed robust long-term memory (LTM) and excitatory postsynaptic current (EPSC) retention in the 2.0 wt% AZO device.

Conclusions:

• Precise control of Al doping in ZnO via the sol-gel method enables effective defect engineering for neuromorphic applications.
• The 2.0 wt% AZO composition offers a promising pathway for developing low-cost, scalable optoelectronic synapses.
• These findings support the advancement of in-sensor computing and neuromorphic vision systems with tunable memory functionalities.