Excitation density dependent carrier dynamics in a monolayer MoS2: Exciton dissociation, formation and bottlenecking

Abstract

Research on Molybdenum Disulfide (MoS2) monolayer at high excitation densities is critical due to its rising demand in optoelectronic applications such as lasers, compact optical parametric amplifiers, and high power detectors. We show that at high excitation densities, measurements on a single monolayer MoS2 reveal a transient response rich in physical processes. Despite the fact that carriers are excited straight to the A-excitonic state, the time and fluence dependence of the observed optical response indicates exciton dissociation followed by hot-carrier generation. In the picosecond time scale, these hot-carriers form excitons, which have a longer lifetime at higher excitation densities, implying a bottlenecking process. For the use of MoS2 at high-excitation densities, the fluence dependency of the relaxation mechanisms detailed here is essential.