Carrier dynamics around nano-scale Schottky contacts studied by femtosecond near-field optics

Summary form only given. We present the first femtosecond near-field (NF) pump-probe measurements of carrier dynamics around nanometer-size tungsten discs embedded in n-doped GaAs. In such samples, Schottky contacts are formed at the tungsten/GaAs interface. Spatially and temporally resolved measurements show that efficient electron trapping into the metal only occurs at higher carrier densities which screen the built-in field, allowing for efficient transport of electrons from the semiconductor towards the metal. These results give new insight into carrier dynamics in metal-semiconductor composite materials in which Schottky contacts are formed.