Study of photoexcited-carrier dynamics in GaAs photoconductive switches using dynamic terahertz emission microscopy

We propose dynamic terahertz (THz) emission microscopy (DTEM) to visualize temporal-spatial dynamics of photoexcited carriers in electronic materials. DTEM utilizes THz pulses emitted from a sample by probe pulses irradiated after pump pulse irradiation to perform time-resolved two-dimensional mapping of the THz pulse emission, reflecting various carrier dynamics. Using this microscopy, we investigated carrier dynamics in the gap region of low-temperature-grown GaAs and semi-insulating GaAs photoconductive switches of the identical-dipole type. The observed DTEM images are well explained by the change in the electric potential distribution between the electrodes caused by the screening effect of the photoexcited electron-hole pairs. (C) 2016 Chinese Laser Press