This study investigates the optoelectronic properties of n-n isotype ${\mathrm{Ga}}_2{\mathrm{O}}_3/\mathrm{Ga}\mathrm{N}$ heterojunctions, demonstrating their potential as light-activated diodes under ultraviolet (UV) spectra. The heterojunction exhibits type II staggered band alignment with a valence-band offset of 1.56 eV and conduction-band offset of −0.16 eV. Under dark conditions, the heterojunction device acts as a double Schottky diode connected back-to-back with asymmetric I-V characteristics. Under UV illumination (254–365 nm), the device transitions from OFF state to a rectifying state, achieving a rectification ratio exceeding ${10}^3$ with a photo-to-dark-current ratio of ≈1.3 × ${10}^3$. This rectification arises from band offset and interface trap states, enabling unidirectional photocurrent flow dominated by thermionic field emission under forward bias. The device also demonstrates high responsivity and functions effectively as a half-wave rectifier for sinusoidal signals, with minimal power consumption (1.76 nW) in the dark. This isotype ${\mathrm{Ga}}_2{\mathrm{O}}_3/\mathrm{Ga}\mathrm{N}$ heterojunction can offer a promising platform for applications in optical logic, secure communication, crosstalk-free UV imaging, and light-triggered switches, advancing the development of high-performance, optically controlled rectifiers.

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• Optoelectronics
• Photoconductivity
• Photocurrent
• Photoinduced effect
• Diodes
• III-V semiconductors
• Junctions
• Transparent conducting oxides