Optical Properties of Low‐Defect Large‐Area Hexagonal Boron Nitride for Quantum Applications

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Intrinsic defects and their concentrations in hexagonal boron nitride (h‐BN) play a key role in single‐photon emission. In this study, the optical properties of large‐area multilayer h‐BN‐on‐sapphire grown by metal‐organic chemical vapor deposition are explored. Based on the detailed spectroscopic characterization using both cathodoluminescence (CL) and photoluminescence (PL) measurements, the material is devoid of random single‐point defects instead of a few clustered complex defects. The emission spectra of the measurements confirm a record‐low‐defect concentration of ≈10 4 cm −2 . Post‐annealing, no significant changes are observed in the measured spectra and the defect concentrations remain unaltered. Through CL and PL spectroscopy, an optically active boron vacancy spin defect is identified and a novel complex defect combination arising from carbon impurities is revealed. This complex defect, previously unreported, signifies a unique aspect of the material. In these findings, the understanding of defect‐induced optical properties in h‐BN films is contributed, providing insights for potential applications in quantum information science.