Enhancement of the deep-levelemission and its chemical origin in hexagonal boron nitride

Defect-related deep-level emissions at similar to 4eV from hexagonal boron nitride (h-BN) have been extensively investigated during the past decades. Although the emission has often been associated with deep level impurities such as carbon and oxygen, the structural and chemical origins of the emission center have not yet been identified. Here, we perform systematic photoluminescence measurements and quantitative trace impurity analysis of variously heat-treated h-BN samples with different deep-level emission intensities. In contrast to the common belief, no positive correlation between the impurity (carbon and oxygen) concentration and the deep-level emission intensity was found. We also demonstrate that the intensity of the deep-level emission is significantly enhanced by high-temperature heating (similar to 1900 degrees C) under an N-2 environment and subsequent post-annealing at similar to 900 degrees C. These results suggest that intrinsic defects created under N-2 -rich conditions are responsible for the deep-level emission. Furthermore, we found that besides the well-recognized zero-phonon line (ZPL) at similar to 4.1 eV, additional ZPLs are induced in the near ultraviolet (NUV) region by appropriate annealing of the N-2-treated h-BN sample. The results of temperature-dependent and time-resolved PL measurements on these NUV emission bands are given and discussed. Published by AIP Publishing.