Epitaxial β‐Ga ₂ O ₃ /GaN Heterojunction Based UV‐C/UV‐A Photodetectors with Superior Responsivity and Stability Under Vertical and Lateral Mode Operations

ABSTRACT We report the development of a high‐performance, bias‐tunable dual‐band ultraviolet photodetector based on a type‐I β‐Ga2O ₃ /GaN heterojunction fabricated by pulsed laser deposition (PLD). The device enables detection of 255 nm and 347 nm through bias control, exhibiting high responsivity and stable performance. Reflection high‐energy electron diffraction, synchrotron X‐ray diffraction, and X‐ray photoelectron spectroscopy confirm the formation of a high‐quality epitaxial β‐Ga2O ₃ /GaN interface with favorable conduction‐ and valence‐band offsets that enhance carrier generation and suppress recombination. The UV detection performance was evaluated in both vertical photodetector (VPD) and lateral photodetector (LPD) configurations. The VPD demonstrates responsivities of 19.8 A/W at 255 nm and 923.6 A/W at 347 nm under a low bias of 5 V, while the LPD achieves 365.7 A/W at 255 nm and 455.1 A/W at 347 nm under 40 V. The enhanced near‐UV response arises from a synergistic mechanism combining photoconductive gain in β‐Ga2O ₃ and band‐edge absorption in GaN, enabled by engineered band alignment. This work establishes a generalizable design strategy for next‐generation dual‐band UV photodetectors for flame detection, space‐based monitoring, environmental safety, and secure communications.