Spatially resolved picosecond luminescence studies of carrier sweep-out photoconductive switches

Summary form only given. We present the first spatially resolved streak camera experiments on semiconductor photoconductive switches. These measurements reveal the temporal evolution of luminescence profiles and the underlying spatio-temporal dynamics of the charge carriers and the electric field. Our data directly visualize that carrier sweep-out can be extremely slow in photoconductive switches produced from high-quality semiconductors in which carrier trapping into defects is negligible. A screening-induced rapid reduction of the electric field and a slow field recovery are at the origin of this dynamics. The long carrier dwell time can severely limit the repetition rate of high-quality semiconductor switches unless the carrier density is properly chosen. Our detailed spatio-temporal measurements provide a solid basis for the validation of numerical models. Such models allow for the optimization of high-quality semiconductor switches, which are often used as ultrafast voltage pulse sources and THz antennas due to their high carrier mobility and, therefore, high output amplitude.