Résumé
I will discuss here our results on phonon-assisted recombination in hBN, from bulk crystals to few-layer samples. First, I will focus on hBN crystals where the combination of isotopic purification, Raman scattering and polarized-resolved photoluminescence allowed us to identify the different phonon modes involved in the efficient phonon-assisted recombination in bulk hBN. In a second part, I will discuss photoluminescence experiments in epilayers grown by high-temperature molecular beam epitaxy. These epilayers have a thickness of few monolayers of hBN, and I will show that phonon-assisted recombination displays a distinct phenomenology with a PL spectrum different from the one of bulk crystals.