Stacking-dependent deep level emission in boron nitride

Abstract

We report hyperspectral microscopy in ${sp}^{2}$-bonded boron nitride polytypes with a simultaneous inspection of the photoluminescence signal in the UV-C and UV-B spectral ranges. By comparing two different polytypes extracted from the same polycrystalline sample, we reveal that the well-known ``4 eV defect'' does not emit at the same energy for polytypes in the $AB$ and $A{A}^{\ensuremath{'}}$ stackings. The zero-phonon line is either at 4.14 or 4.16 eV for the noncentrosymmetric $AB$ stacking, instead of the usual 4.09 eV energy in the $A{A}^{\ensuremath{'}}$ stacking. Our results open the way for different characterization methods of the stacking order in ${sp}^{2}$-bonded boron nitride, and bring alternative inputs for the elucidation of the atomistic configuration of points defects by advanced ab initio calculations.