Ultrafast carrier dynamics in semiconductor nanowires

Semiconductor nanowires (NWs) are nanostructures with a number of novel optical and electronic properties that offer great promise for applications in areas including nanoelectronics, thermoelectrics, sensing, and nanophotonics. To realize the full potential of these unique nanosystems, however, a deep understanding of their response to optical excitation on a sub-picosecond time scale is required. Here, we review recent ultrafast optical studies of carrier dynamics in semiconductor NWs. These experiments have been performed on different materials as a function of both intrinsic NW parameters such as diameter and doping as well as experimental parameters including photoexcited carrier density and wavelength. A variety of phenomena, including one-dimensional (1D) exciton dynamics, rapid carrier trapping at surface and bulk defects, and lasing from an electron-hole plasma (EHP) have been observed. These first measurements of ultrafast carrier dynamics are a tantalizinghint of the rich physics yet to be discovered in these quasi-1D systems. Ultrafast optical spectroscopy can track the temporal evolution of carrier populations in semiconductor NWs with femtosecond time resolution.