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• The DUV optoelectronic synapse was fabricated on the MOCVD-deposited a-GaO x film. • The information written into the bionic synapse is non-volatile. • The synapse can mimic the transition from short-term memory to long-term memory. Optoelectronic bionic synapses, integrating sensing and processing capabilities, help to break through the limitations of von Neumann structure and are promising in smart sensors, AI robots etc. fields. Here, we fabricated a deep ultraviolet (DUV) optoelectronic bionic synapse with an amorphous gallium oxide (a-GaO x) film deposited by metal–organic chemical vapor deposition (MOCVD). DUV illumination pulses could be facilely written into the bionic synapse, and the written information exhibits non-volatility. By manipulating the illumination pulse number, the pulse width, and the pulse power density, the synapse is capable of transitioning from short-term memory (STM) to long-term memory (LTM), effectively emulating the learning-memory behavior of human brains. [ABSTRACT FROM AUTHOR]

[Display omitted] • The surface chemical composition of β-Ga 2 O 3 films is discussed in depth. • The component of O 1s with the binding energy around 531.8 eV is attributed to surface lattice O atoms. • The defects inside the β-Ga 2 O 3 films were analyzed by HRTEM. β gallium oxide (β-Ga 2 O 3) is an ultrawide bandgap semiconductor with great potential for solar-blind ultraviolet detection, power devices, and gas sensing. However, the understanding of the surface properties of β-Ga 2 O 3 remains insufficient. Here, epitaxial growth of β-Ga 2 O 3 films was carried by metal–organic chemical vapor deposition (MOCVD) on sapphire substrates. The surface chemical composition, surface layer crystalline properties, and surface morphology of the β-Ga 2 O 3 films were discussed and analyzed in detail. By comparing the atomic ratios of O/Ga, the surface morphology, and the crystalline properties of the films, we attribute the component of O 1s with the binding energy around 531.8 eV to surface lattice O atoms. Moreover, the one-dimensional defects inside the surface layers and the near-interface regions of the films were observed at atomic scale by high resolution transmission electron microscopy (HRTEM). By comparing the lattice fringes of different facets, the geometric phase uniformity, and the distribution of strain, we found that the crystalline quality of the surface layers is much higher than the near-interface regions. [ABSTRACT FROM AUTHOR]