Formation dynamics of excitons and temporal behaviors of fano resonance due to the exciton-impurity-phonon configuration interaction in ZnO

Formation dynamics of free and neutral donor bound excitons (FX and D 0X) in a high quality ZnO single crystal are studied by means of time-resolved photoluminescence (TRPL) at various temperatures. At low-temperatures, FX and D 0X formation times are determined to be ∼5 and ∼10 ps, respectively, by fitting the rise process with the Boltzmann sigmoidal function. Temporal information of FX- and D 0X-longitudinal optical (LO) phonon coupling is also acquired by measuring TRPL spectra of the first-order LO phonon-assisted FX and D 0X transitions. In particular, interesting time evolution of luminescence intensity in the Fano resonance region due to the configuration interaction of exciton-impurity-phonon is explored. © 2011 American Chemical Society

Electronic band structures and electron spins of InAs/GaAs quantum dots induced by wetting-layer fluctuation

Electronic band structures and spin states of the InAs/GaAs quantum dots (QDs) induced by the wetting-layer fluctuation were investigated by employing the technique of time-resolved Kerr rotation (TRKR) with and without magnetic field. Sign change of the Kerr rotation signal was unambiguously observed when only the wavelength of the pump/probe light was scanned. By carefully examining the dependence of TRKR signal on the excitation wavelength and magnetic field as well as photoluminescence and reflectance spectra, the physical origin causing the sign change of the Kerr signal is uncovered. It is due to the resonant excitations of electrons with opposite spin orientations at heavy- (hh) and light-hole (lh) subbands, respectively, since there is a large enough energy separation in QDs for the excitation laser pulses. This measurement also leads to a precise determination of the energy separation between the hh and lh subbands near k 0 point in the dots. \ua9 2011 American Institute of Physics.Peer reviewed: YesNRC publication: Ye