Single‐Photon Emitters in β‐Ga 2 O 3 at Distinct Excitation Energies: Defect Origin and Photophysical Properties

ABSTRACT Room‐temperature single‐photon emission in beta‐phase gallium oxide (β‐Ga 2 O 3 ) extends the application scope of this ultra‐wide bandgap semiconductor beyond power electronics, opening up the possibility of using it as a quantum light source platform. However, the rich and complex defect landscape of β‐Ga 2 O 3 makes identifying the microscopic origins of these emitters a major challenge. Herein, by combining in situ confocal photoluminescence mapping, multi‐wavelength excitation, and first‐principles density functional theory calculations, we identify a new single‐photon emitter (SPE) excited by blue (405 nm) light. The 405 nm‐excited emitters exhibit high purity, excellent photostability, and a high Debye‐Waller factor. They originate from the neutral V GaI ‐V OI divacancy, which differs from the previously reported 532 nm‐excited one (V GaI ‐V OIII ). The two emitter types show largely non‐overlapping spatial distributions and different optical properties. Cross‐excitation cycles reveal that 405 nm illumination can partially bleach the 532 nm‐excited emitters via a photoionization process, while the reverse effect is much weaker. Our findings provide a clear defect origin for this new blue‐excited SPE in β‐Ga 2 O 3 and establish a multi‐wavelength strategy to discriminate distinct defect populations, paving the way for defect engineering in ultra‐wide‐bandgap semiconductor quantum photonics.