PICOSECOND AND STEADY-STATE SPECTROSCOPY OF THE WURTZITE SEMIMAGNETIC SEMICONDUCTOR CADMIUM(1-X)MANGANESE(X)SELENIDE (ENERGY RELAXATION, SPIN)

The kinetics of a non-equilibrium photogenerated electron-hole plasma in CdSE is investigated using picosecond time resolved spectroscopy at room temperature. Based on the fact that the polar optical phonon emission rate is reduced due to screening by the high density of e-h plasma, the remaining dominant mechanism for hot carrier cooling is the non-polar optical phonon emission even though CdSE is a highly polar semiconductor. Rapid plasma expansion has been proposed as a possible explanation for much lower estimated carrier densities on the grounds of the observed larger spatial width of the photoluminescence relative to the laser spatial width, moderate change of Auger recombination rate with the excitation fluence, the absence of an observed change in the Fermi level with increased excitation intensity and earlier formation of excitons after the picosecond pulse (5 psec) excitation at a low temperature (12K). Large values of the diffusion constant are explained in terms of a screened electron-phonon interaction.; Picosecond time resolved spin relaxation kinetics of high density free carriers is investigated at low temperatures in CdSe (x = 0) and in the dilute semimagnetic semiconductor Cd(,1-x)Mn(,x)Se for x = 0.05 and 0.10. The fast spin relaxation observed in CdSe results from a mechanism associated with the noncentrosymmetric character of the band structure of this material. The spin relaxation times are <20 psec in Cd(,1-x)Mn(,x)Se and are consistent with spin flip Raman scattering measurements. The increase in spin relaxation rate relative to CdSe is explained in terms of the spin exchange between the carriers and the magnetic spin sites.; Using steady state photoluminescence from Cd(,1-x)Mn(,x)Se (0 (LESSTHEQ) x (LESSTHEQ) 0.86), we were able to measure the optical deformation potentials of the conduction band (0.5 x 10('9) eV/cm) and valence band (0.24 x 10('9) eV/cm) in CdSe. The temperature dependent additional bound excitonic binding energy was attributed to the formation of a bound magnetic polaron (h-BMP) at low temperature. The h-BMP formation times are (TURN)340 psec in Cd(,0.95)Mn(,0.05)Se and (TURN)90 psec in Cd(,0.9)Mn(,0.1)Se. These times corresponding to the formation of the BMP from the bound excitons which themselves are formed (TURN)185 psec after the picosecond excitation pulse.