Ultrafast carrier capture dynamics in InGaAs∕GaAs quantum wires

We use time-resolved terahertz-pulse spectroscopy to study the ultrafast carrier dynamics in InGaAs∕GaAs (311)A quantum wires. Anisotropy in the photoconductive dynamics is observed when aligning the terahertz probe polarization parallel versus perpendicular to the wire direction. The origin of this anisotropy is the carrier capture into localized quantum-wire states from delocalized wetting layer or barrier regions over time scales from 6to30ps. The capture efficiency is found to be strongly temperature dependent, with thermal emission dominating above 125K, while state-filling effects within the wires influence the capture rate below 125K. Transient spectroscopy reveals a Drude-like carrier conductivity.