Spin-Polarized Localized Exciton Photoluminescence Dynamics in GaInNAs Quantum Wells

We have investigated spin polarization-related localized exciton photoluminescence (PL) dynamics in GaInNAs quantum wells by time-resolved PL spectroscopy. The emission energy dependence of PL polarization decay time as well as polarization-independent PL decay time suggests that the acoustic phonon scattering in the process of localized exciton transfer from the high-energy localized states to the low-energy ones dominates the PL polarization relaxation. By increasing the excitation power from 1 to 10 mW, the PL polarization decay time is changed from 0.17 to more than 1 ns, which indicates the significant effect of the trapping of localized electrons by nonradiative recombination centers. These experimental findings indicate that the spin-related PL polarization in diluted nitride semiconductors can be manipulated through carrier scattering and recombination process. (C) 2009 The Japan Society of Applied Physics

High-temperature electron-hole liquid and dynamics of Fermi excitons in a In0.65Al0.35As/Al0.4Ga0.6As quantum dot array

State-filling effects of the exciton in a In0.65Al0.35As/Al0.4Ga0.6As quantum dot array are observed by quantum dot array photolumineseence at a sample temperature of 77 K. The exciton emission at low excitation density is dominated by the radiative recombination of the states in the s shell and at high excitation density the emission mainly results from the radiative recombination of the exciton state in the p shell. The spectral interval between the states in the s and p shells is about 30-40 mcV. The time resolved photoluminescence shows that the decay time of exciton states in the p shell is longer than that of exciton states in the s shell, and the emission intensity of the exciton state in the p shell is superlinearly dependent on excitation density. Furthermore, electron-hole liquid in the quantum dot array is observed at 77 K, which is a much higher temperature than that in bulk. The emission peak of the. recombination, of electron-hole liquid has an about 200 meV redshift from the exciton fluorescence. Two excitation density-dependent emission peaks at 1.56 and 1.59 eV are observed, respectively, which result from quantum confinement effects in QDs. The emission intensity of electron-hole liquid is directly proportional to the cubic of excitation densities and its decay time decreases significantly at the high excitation density.

Dynamics of quantum dissipation systems interacting with fermion and boson grand canonical bath ensembles: Hierarchical equations of motion approach

A hierarchical equations of motion formalism for a quantum dissipation system in a grand canonical bath ensemble surrounding is constructed on the basis of the calculus-on-path-integral algorithm, together with the parametrization of arbitrary non-Markovian bath that satisfies fluctuation-dissipation theorem. The influence functionals for both the fermion or boson bath interaction are found to be of the same path integral expression as the canonical bath, assuming they all satisfy the Gaussian statistics. However, the equation of motion formalism is different due to the fluctuation-dissipation theories that are distinct and used explicitly. The implications of the present work to quantum transport through molecular wires and electron transfer in complex molecular systems are discussed. (c) 2007 American Institute of Physics.

Non-exponential photoluminescence decay dynamics of localized carriers in disordered InGaN/GaN quantum wells: the role of localization length

In this article, we report a combined experimental and theoretical study on the luminescence dynamics of localized carriers in disordered InGaN/GaN quantum wells. The luminescence intensity of localized carriers is found to exhibit an unusual non-exponential decay. Adopting a new model taking the radiative recombination and phonon-assisted hopping transition between different localized states into account, which was recently developed by Rubel et al., the non-exponential decay behavior of the carriers can be quantitatively interpreted. Combining with precise structure characterization, the theoretical simulations show that the localization length of localized carriers is a key parameter governing their luminescence decay dynamics. (c) 2006 Optical Society of America.

Effect of nonradiative recombination on carrier dynamics in GaInNAs/GaAs quantum wells

The nonradiative recombination effect on carrier dynamics in GaInNAs/GaAs quantum wells is studied by time-resolved photoluminescence (TRPL) and polarization-dependent TRPL at various excitation intensities. It is found that both recombination dynamics and spin relaxation dynamics strongly depend on the excitation intensity. Under moderate excitation intensities the PL decay curves exhibit unusual non-exponential behaviour. This result is well stimulated by a rate equation involving both the radiative and non-radiative recombinations via the introduction of a new parameter of the effective concentration of nonradiative recombination centres in the rate equation. In the spin dynamics study, the spin relaxation also shows strong excitation power dependence. Under the high excitation power an increase of spin polarization degree with time is observed. This new finding provides a useful hint that the spin process can be controlled by excitation power in GaInNAs systems.

Nonradiative recombination effect on photoluminescence decay dynamics in GaInNAs/GaAs quantum wells

The influence of nonradiative recombination on the photoluminescence (PL) decay dynamics in GaInNAs/GaAs quantum wells is studied by time-resolved photoluminescence under various excitation intensities. It is found that the PL decay process strongly depends on the excitation intensity. In particular, under the moderate excitation levels the PL decay curves exhibit unusual nonexponential behavior and show a convex shape. By introducing a new parameter of the effective concentration of nonradiative recombination centers into a rate equation, the observed results are well simulated. The cw PL data further demonstrate the nonradiative recombination effect on the optical properties of GaInNAs/GaAs quantum wells. (c) 2006 American Institute of Physics.

Exciton dynamics in self-organized InAs/GaAs quantum dots

Using a newly-developed population mixing technique we have studied the exciton dynamics in self-organized InAs/GaAs quantum dots (QDs). It is found that the exciton lifetime in self-organized InAs/GaAs QDs is around 1 ns, almost independent of InAs layer thickness. The temperature dependence of the exciton lifetime varies from sample to sample, but no obvious experimental evidence was found that the lifetime is related to the delta-function of density of states in QDs. We have also found that the population mixing technique can be used to directly reveal the band-filling effect in the excited states of the QDs.

Nonradiative recombination effect on photoluminescence decay dynamics in GaInNAs/GaAs quantum wells - art. no. 61180Z

The nonradiative recombination effect on the photoluminescence (PL) decay dynamics in GaInNAs/GaAs quantum wells is studied by photoluminescence and time-resolved photoluminescence under various excitation intensities and temperatures. It is found that the PL decay dynamics strongly depends on the excitation intensity. In particular, under the moderate excitation levels the PL decay curves exhibit unusual non-exponential behavior and show a convex shape. By introducing a new concept of the effective concentration of nonradiative recombination centers into a rate equation, the observed results are well simulated. In the cw PL measurement, a rapid PL quenching is observed even at very low temperature and is of the excitation power dependence. These results further demonstrate that the non-radiative recombination process plays a very important role on the optical properties of GaInNAs/GaAs quantum wells.

Dynamics of Cavity Polaritons in a GaAs Quantum-well Semiconductor Microcavity

To provide the dynamics of cavity polariton in semiconductor microcavity containing GaAs quantum-well, the dispersions of the three cavity polaritons have been given by the model of three coupled oscillators, meanwhile the linewidths, group velocities and the mass of the three cavity polaritons have been demonstrated. The results indicated that because of the weight occupied by the photon, heavy hole exciton and light hole extiton in the three cavity ploariton the cavity polaritons exhibited different dynamic behaviors.

Isospin- and momentum-dependent interaction in isospin-dependent quantum molecular dynamics

An isospin-dependent quantum molecular dynamical model (IQMD) is developed, with the isospin degree of freedom in the momentum-dependent interaction(MDI) included in IQMD, to obtain an isospin- and momentum-dependent interaction (IMDI) in IQMD. We investigate the effect of IMDI on the isospin fractionation ratio and its dynamical mechanism in the intermediate energy heavy ion collisions. It is found that the IMDI induces the significant reductions in the isospin fractionation ratio for all of beam energies, impact parameters, neutron-proton ratios and mass number of colliding systems. However, the strong dependence of isospin fractionation ratio on the symmetrical potential is preserved, with the isospin degree of freedom included in the MDI, i.e. the isospin fractionation ratio is still a good probe for extracting the information about the equation of state of isospin asymmetrical nuclear matter.

Effects of the transition dipole moment function on the dynamics of ozone photodissociation: an exact 3D quantum mechanical study

The effects of the transition dipole moment function (TDMF) on the dynamics Of O-3 photodissociation in the Hartley band have been exploited by means of exact 3D time-dependent wavepacket method using the SW potential energy surface [J. Chem. Phys. 78 (1983) 7191]. The calculations show that the explicit inclusion of the TDMF results in slight uniform reductions for the intensities of recurrence peaks of the autocorrelation function and a slight broadening of the absorption spectrum, in comparison with the result where the TDMF is assumed to be constant. The pattern of recurrence structures of the autocorrelation function is essentially unaffected. (C) 2001 Elsevier Science B.V. All rights reserved.