Auger Recombination Kinetics of the Free Carriers in Hexagonal Boron Nitride

Hexagonal boron nitride (hBN) is a wide indirect bandgap semiconductor with a strong luminescence that is many orders of magnitude higher than diamond. It holds great promise for optoelectronic devices over a wide frequency range spanning from ultraviolet (UV) to mid-infrared (IR). Auger recombination, a nonradiative mechanism, is one of the three mechanisms that determine the kinetics of the photoexcited carriers and strongly contributes to losses in quantum efficiency. Here, we report on the dynamics of photogenerated free carriers in exfoliated 10B-enriched (99%) hBN at room temperature. We identified Auger and defect-assisted recombination mechanisms experimentally by utilizing ultrafast transient absorption spectroscopy. Recombination at high carrier densities occurs via an Auger process with a characteristic rate constant in the range of 10–24 to 10–26 cm6/s with a strong dependence on the excitation fluence. A slower recombination mechanism independent of the excitation fluence at a rate of ∼5.6 × 109 s–1 was assigned to Shockley–Read–Hall (SRH) defects.