Surface plasmons regulate photon absorbance, photo response and carrier injection in Ga₂O₃ photodetectors

Ultrawide bandgap semiconductor gallium oxide (Ga_2O_3), with a natural bandgap of approximately 4.9 eV, has been extensively utilized in constructing solar-blind deep ultraviolet (DUV) photodetectors. To address the persistent challenges of high dark current and low photoresponsivity, metal nanostructured surface plasmons have been introduced to generate localized electric fields, thereby enhancing photodetection performance. Incident photons excite hot electrons within the metallic structures, which are subsequently injected into the photoactive semiconductor layer. When the resonance peak of the plasmonic structure matches the absorption peak of Ga_2O_3 layer, localized surface plasmon resonance (LSPR) significantly boosts photon absorption and responsivity. Concurrently, the localized interfacial barrier restricts carrier transport, effectively suppressing dark current. This enhancement stems from charge density oscillations within the metallic nanoparticles, facilitating strong plasmon-exciton coupling. In this review, we systematically discuss Ga_2O_3-based solar-blind DUV photodetectors decorated with metal nanostructures, covering photoconductive, array, and heterojunction architectures. Furthermore, advances in broadband detection mechanisms, complex plasmonic designs, and subwavelength optics are explored. Compared with conventional devices, plasmon-enhanced photodetectors typically exhibit responsivity improvements from \sim 0.1 A/W to over tens of A/W and reduced dark current by 1-2 orders of magnitude. Finally, current challenges and future perspectives are outlined. However, challenges such as poor controllability of nanoparticle distribution, stability issues, and the trade-off between enhanced responsivity and increased noise remain to be addressed.