Spin injection through magnetic/nonmagneticheterointerfaces using trions for spin detection

摘要

Spin-polarized electron optical injection through a non-magneticCdMgTe semiconductor layer has been studied. Cd0.33Mg0.24Mn0.03Te dilutedmagnetic semiconductor was used as a spin-injecting layer. We exploit theunique feature of trions, I.e., charged excitons, as objects for sensitive opticaldetection of the spin injection into a quantum well separated from the injectorby a graded gap Cd0.76Mg0.24Te. CW and time resolved magneto-opticalmeasurements under different selective excitations below and above the bandgap of the Cd0.33Mg0.24Mn0.03Te spin aligner have been performed. The resultsshow that at small fields the ratio of the density of X-s, negatively chargedexcitons in the singlet state, and the neutral exciton, X0, is large when the lightis absorbed only in the quantum well, and it becomes smaller when theabsorption occurs in the non-magnetic barrier. It is re-enhanced significantlywhen the absorption is being in the magnetic spin polarized layer. The latterfinding indicates that electron spins do not lose completely their initialpolarization during their transport through a layer with an opposite sign of gfactorinto CdTe QW.