Thermally oxidized gallium nitride for photo-neuromorphic devices

Thermal oxidation of wide-bandgap semiconductors offers a simple yet underexplored route to functionalize emerging optoelectronic devices. Here, we demonstrate that thermally oxidized gallium nitride metal-oxide-semiconductor (MOS) capacitors, in which oxidation forms a β-Ga2O3/GaN heterostructure, can operate as photo-neuromorphic devices. The resulting structures exhibit pronounced persistent photocapacitance, enabling the emulation of synaptic plasticity and experiential learning under optical stimulation while maintaining zero static power consumption. When integrated into an in-sensor physical reservoir computing framework, the devices achieve a classification accuracy of 89.8% on the Modified National Institute of Standards and Technology handwritten dataset using 5-bit temporal encoding. These findings establish thermal oxidation as a scalable strategy for realizing capacitance-type photo-neuromorphic devices and position thermally oxidized GaN MOS capacitors as a promising platform for vision-inspired neuromorphic computing.