Cluster Engineering for Photoconductive Switches

摘要: Molecular beam epitaxy (MBE) of arsenides such as GaAs or AlGaAs with typical group III and As fluxes, but a substrate temperature in the range 200°C to 300°C, results incorporation excess epilayer;1 annealing at temperatures 600°C higher causes precipitate.2–5 The final average size corresponding density clusters is controlled by duration anneal,6–7 while amount epilayer during MBE.8 This composite material, consisting semi-metallic semiconductor matrix, exhibits very interesting electrical optical properties. semi-insulating due internal Schottky barriers associated clusters.9,10 In addition, reasonable mobilities some cases sub-picosecond lifetimes, making it an attractive material high-speed photoconductor.11–15 lifetime photogenerated carriers dependent on spacing can be tuned from less than 200 fs over 10 ps anneal.16 varies square between precipitates, which indicates may diffusion precipitates where they recombine. when used photoconductive switch generate detect freely propagating bursts electromagnetic radiation, radiated intensity increases either growth temperature17 anneal temperature, indicating increase carrier mobilites. this paper we present details control these composites use launch pulses. introduce technique form using ion-implantation metals—such Fe Ni—into subsequent nucleate clusters.