Spin lifetime from the Hanle effect and fine structure of excitonic levels in InAlAs/AlGaAs quantum dots
Résumé
Excitation of electron-hole pairs by circularly polarized light yields an electron spin polarization in InAlAs self-assembled quantum dots. This spin polarization causes circular polarization of the photoluminescence light, its degree decreasing in a magnetic field perpendicular to the initial spin vector of the electron-hole pair (Hanle effect). The scaled spin lifetime g(perpendicular to)(e)T(s), where g(perpendicular to)(e) is the transverse electron Lande factor and T-s is the electron spin lifetime is deduced from the Hanle curves and is of the order of 100 ps. It is attributed to the polarized spin confined in quantum dots. With increasing energy detection the width of the Hanle curve is reduced. The corresponding scaled electron-hole spin lifetime increases with increasing energy detection. We have also performed photoluminescence study of excitons localized in InAlAs quantum dots, in a longitudinal magnetic field. The magnetic-field dependence of the linear and circular polarization evidences the exciton fine structure and helps to determine the anisotropic part of the exciton exchange, which is of the order of 14 mu eV. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.