Colour centres in hexagonal boron nitride (hBN) have emerged as intriguing contenders for integrated quantum photonics. In this work, we present detailed photophysical analysis of hBN single emitters emitting at the blue spectral range. The emitters are fabricated by different electron beam irradiation and annealing conditions and exhibit narrow-band luminescence centred at 436 nm. Photon statistics as well as rigorous photodynamics analysis unveils potential level structure of the emitters, which suggests lack of a metastable state, supported by a theoretical analysis. The potential defect can have an electronic structure with fully occupied defect state in the lower half of the hBN band gap and empty defect state in the upper half of the band gap. Overall, our results are important to understand the photophysical properties of the emerging family of blue quantum emitters in hBN as potential sources for scalable quantum photonic applications.

Nitrogen (N) is a promising candidate currently being pursued for p-type doping in Ga2O3. In this work, the results of detailed investigations into N-doped β-Ga2O3 nanowires using microstructural, chemical, and optical analyses are described. Monoclinic β-Ga2O3 nanowires are grown by chemical vapor deposition using a metallic gallium (Ga) precursor and subsequently doped with N by remote plasma by exploiting their nanoscale cross sections and large surface-to-volume ratios. The N incorporation into β-Ga2O3 is confirmed by X-ray absorption near-edge and Raman spectroscopies without changes in the nanowire morphology. N is found to exist mainly as molecular N2 and N–O chemical states, but a significant portion of N substitutes on oxygen (O) sites. Concurrent temperature-resolved cathodoluminescence measurements of the undoped and N-doped β-Ga2O3 are used to track the temperature dependences of their intrinsic ultraviolet (UV) luminescence and defect-related visible bands from 80 to 480 K. The blue and green bands increase in intensity relative to the UV after N doping; however, their intensity variations with temperature are found to be identical for the undoped and N-doped β-Ga2O3, indicating that these bands originate from existing recombination pathways in Ga2O3 rather than from radiative N-related centers. The enhancement in defect-related luminescence in N-doped β-Ga2O3 is explained by an increase in the concentration of O vacancies as a result of the compensation of NO acceptors.

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