High-density photogenerated free-carrier spin relaxation processesin Wurtzite semiconductors: CdSe and semimagnetic semiconductorCd1-xMnxSe

Picosecond time-resolves spin relaxation kinetics of high-density free carriers is investigated at low temperatures on CdSe (x=0) and in the dilute semimagnetic semiconductor Cd_1-xMn_x Se for x=0.05 and 0.10. The fast spins relaxation observed in CdSe results from a mechanism associated with the noncentrosymmetric character of the band structure for this material. This process is similar to the one proposed by M.I. D'yakonov and V.I. Perel' (1971) for the zinc blende crystal structures. The spin relaxation times in CdSe are on the order of 30 ps. The spin relaxation time are <20 ps in semimagnetic semiconductor Cd_1-xMnSe and are consistent with spin-flip Raman scattering measurements. The increase in spin relaxation rate relative to CdSe is explained in terms of the carrier spin exchange between the carriers and the magnetic spin sites. A probable cause for the reduction in the observed spin polarization factor for carriers in Cd_1-xMn_xSe ( x≠0) is presented