Negative circular polarization of InP QD luminescence: Mechanism of formation and main regularities

The spectrum and kinetics of the circular polarization of InP quantum dot (QD) photoluminescence have been experimentally investigated under different conditions of optical excitation and at different bias voltages applied to the sample. It is established that, at a bias of about -0.1 V, the degree of photoluminescence polarization is negative and reaches -50% in limiting cases. It is concluded that the negative polarization is formed in QDs containing one recident electron per dot and is mainly caused by the optical orientation of the electron spin. It is shown that all experimentally observed regularities are well described in the framework of the model assuming the energy relaxation of photogenerated electron-hole pairs accompanied by the electron- hole spin flip-flop process.