Abstract

Picosecond time resolved spin relaxation kinetics of high density free carriers is investigated from luminescence at low temperatures in CdSe (x=0) and in dilute in the semimagnetic semiconductor Cd_1−xMn_xSe for x=0.05 and 0.10. The fast spin relaxation observed in CdSe results from a mechanism associated with the non-centrosymmetric character of the band structure for this material. This process is similar to the one proposed by D'yakonov and Perel' (D-P) for the zinc blende crystal structures. The spin relaxation times in CdSe are of the order of 30 psec and the observed spin polarization factor for carriers in CdSe is in good agreement with theory. The spin relaxation times are < 20 psec in Cd_1−xMn_xSe 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. The carrier spin exchange with magnetic spin sites and the D-P process inherent in the host crystal are equally important in semimagnetic semiconductors. The spin polarization factor at t=0, ρ₁(0), obtained in CdSe is ~ 50% using one photon excitation, while for Cd_0.95Mn_0.05Se and Cd_0.9Mn_0.1Se the values (ρ₂(0)) are ≈ 18% and ≈ 28% using two photon excitation.

© 1986 Optical Society of America