Optical gap and optically active intragap defects in cubic BN

Studies on the optical properties of cubic BN are generally hindered by the very high density of crystal defects. Thus, the precise value of its optical gap is still debated, with large discrepancies between reported theoretical and experimental estimated values. In this study we addressed open questions of the cubic BN optics by employing high spatially resolved spectroscopy techniques to the highest-quality samples available and combining these observations with state-of-the-art quasiparticle calculations.