Room-temperature ultrafast carrier and spin dynamics in GaAs probed by thephotoinduced magneto-optical Kerr effect - art. no. 235201

The picosecond and subpicosecond dynamics of spins in intrinsic and n-doped GaAs is investigated at room temperature using the time-resolved, pump and probe, photoinduced, near-resonant magneto-optical Kerr effect between 1.4 4 and 1.63 eV. Three components with different temporal ind spectral behavi or are distinguished in both Kerr rotation and ellipticity, and their origi n is discussed in relation with theoretical predictions and simulations. Tw o contributions are attributed to the splitting of the spin sublevels. The first one, present only as long as pump and probe pulses coincide in time, is a coherent response accounted for in terms of the optical Stark effect, whereas the longer decay of the second one, up to 35 ps, is attributed to e lectron spin relaxation. The third component is assumed to arise from the d ifference in population of the photoexcited states and decays within a time smaller than the pulse duration, which is attributed to the energy relaxat ion of electrons towards the bottom of the conduction band through carrier- carrier and carrier-phonon scattering.