Ultrafast Dynamics of Exciton Formation in Semiconductor Nanowires

Abstract The dynamics of free electron–hole pairs and excitons in GaAs–AlGaAs–GaAs core–shell–skin nanowires is investigated using femtosecond transient photoluminescence spectroscopy at 10 K. Following nonresonant excitation, a bimolecular interconversion of the initially generated electron–hole plasma into an exciton population is observed. This conducting‐to‐insulating transition appears to occur gradually over electron–hole charge pair densities of 2–4 × 10¹⁶ cm⁻³. The smoothness of the Mott transition is attributed to the slow carrier‐cooling during the bimolecular interconversion of free charge carriers into excitons and to the presence of chemical‐potential fluctuations leading to inhomogeneous spectral characteristics. These results demonstrate that high‐quality nanowires are model systems for investigating fundamental scientific effects in 1D heterostructures.