Ultrafast carrier dynamics around nanoscale Schottky contacts studied by femtosecond far- and near-field optics

Far- and near-field femtosecond pump–probe spectroscopy has been used to study ultrafast carrier dynamics in matrices of nanometer-scale tungsten disks embedded in GaAs. These studies reveal the dynamics of carrier transfer from a semiconductor into embedded metal clusters in the presence of Schottky contacts and built-in electric fields. The carrier transfer involves transport towards and trapping into the tungsten disks. We find picosecond time constants at higher carrier densities when the built-in field is screened, allowing for efficient carrier transport. Near-field measurements reveal the spatial variation of carrier dynamics. The spatially averaged dynamics can be controlled by the tungsten disk spacing.