Charge carrier scattering and ultrafast Auger dynamics in two-dimensional superatomic semiconductors

Superatom solids are promising for optoelectronic applications, owing to their tunable structural and electronic properties; yet, the electronic transport properties of these materials have been largely unexplored. Here, we report the Auger recombination dynamics of free carriers in two representative two-dimensional superatomic semiconductors, Re6Se8Cl2 and Mo6S3Br6, studied using ultrafast terahertz photoconductivity measurements. The fast Auger recombination dynamics are characterized by a cubic dependence of the Auger rate on carrier density in Re6Se8Cl2 and a quadratic dependence in Mo6S3Br6. The effective lifetimes of Mo6S3Br6 (∼ 0.5 ps) are over an order of magnitude shorter than those (∼ 20 ps) of Re6Se8Cl2. These results highlight the variability of the optoelectronic properties of different superatom solids.