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Abstract

The ultrafast carrier and lattice dynamics in polar and ferromagnetic semiconductors were investigated using optical and X-ray free-electron laser. In polar semiconductor Li-doped CdTe, the influence of Coulomb screening and phonon-plasmon coupling in carrier and lattice dynamics was observed by means of a time resolved pump-probe reflectivity technique. When doping polar semiconductors with magnetic atoms, magnetic interactions are introduced, e.g., in ferromagnetic semiconductor Ga$_{1-x}$Mn$_{x}$As, the Mn doped GaAs. By applying the novel X-ray free-electron laser radiation, delivered by the Linac Coherent Light Source (LCLS), the time resolved X-ray diffraction was measured, which directly reveals the interplay between the laser excited carriers, acoustic phonon modes and spin order. Simultaneously, the evolution of hole quasi Fermi-level as a function of time and temperature was measured by the resonant X-ray emission spectroscopy.