Predominantly radiative recombination in rhombohedral and hexagonal BN up to room temperature

Boron nitride (BN) is a 2D layered material with a honeycomb structure similar to graphene. It has a wide bandgap of approximately 6 eV and hosts color centers that are very bright emitters in the UV range. We present an investigation of time-resolved photoluminescence (PL) spectroscopy of two types of color centers: C300 and C380, which emit at 4.1 and 3.2 eV, respectively. They are C2 and probably cis-C4 defects. It has been found that both these centers have stable PL lifetimes, which practically do not change with temperature in the 4–400 K range. This means that recombination in this range is predominantly radiative, with no thermally activated escape of carriers. The PL lifetimes are about 1 ns and about 1.6 ns for the C300 and the C380, respectively. Most of the investigated samples were grown using metal-organic vapor phase epitaxy and included the two most popular polytypes of the layered BN: rhombohedral and hexagonal. Both polytypes exhibit similarly long PL lifetimes for the studied defects, and both are temperature insensitive. This feature is very important for optoelectronic applications of BN, including single-photon emitters.