The straight bandgap of gallium oxide (GaO₃) is roughly 4.9 eV, making it an ultra-wide bandgap semiconductor. It is a promising candidate for use in ultraviolet (UV) phototransistors and neuromorphic computing systems due to its unique physical and chemical characteristics. With an emphasis on their material properties, device topologies, and photocurrent generating techniques, this chapter provides a thorough introduction of GaO₃—based phototransistors. The relationship between photocurrent intensity and binding energy levels as determined by X-ray photoelectron spectroscopy (XPS) and the improvement of device performance through defect engineering are highlighted. Then, we investigate Ga₂O₃ optoelectronic synapses that resemble biological synaptic plasticity, emphasizing optically modulated spike-timing-dependent plasticity (STDP). There is discussion of MATLAB and Python simulation techniques as well as viewpoints on integrating GaO₃ devices into useful neuromorphic systems. GaO₃ is positioned as a promising material substrate for next-generation neuromorphic and photonic computing technologies by addressing issues like device variability and integration obstacles in the chapter’s conclusion.