4:45 PM - 5:00 PM
[21p-B201-12] Recombination dynamics of indirect excitons in hexagonal BN epilayers containing polytypic segments grown by CVD using carbon-free precursors
Keywords:semiconductor, stacked 2D layers, hBN
Hexagonal (h) BN is a semiconductor that crystallizes in layers of a two-dimensional sp2-bonded honeycomb structure. Since hBN exhibits high quantum efficiency near-band edge emission at around 5.8 eV in spite of the indirect bandgap, hBN has a potential for the use in deep ultraviolet light emitters. For elucidating the emission dynamics of indirect excitons (iXs) in hBN, spatially and temporally resolved luminescence measurements were carried out on hBN epilayers grown using carbon-free precursors. In addition to major lm-side flat-topped (0001) hBN columnar grains, sub-um-scale polytypic segments were identified. The hBN domains exhibited predominant emissions of phonon-assisted fundamental iXs at 5.7–5.9 eV and a less-pronounced 4.0-eV emission band. The photoluminescence lifetime for the iX emissions was 54 ps, which most likely represents the midgap recombination lifetime for an iX reservoir. Because the PL lifetime did not change while the cw intensity increased with temperature above 100 K, both the immobile character of iXs and strong exciton–phonon interaction seem significant for procreating the high efficiency. Equally significant emissions at 6.035 eV at 12 K and 6.0–6.1 eV at 300 K were observed from the polytypic segments, most probably graphitic bernal BN (6/6/2022 APL Featured Article).