29 research outputs found
Competition between radiative decay and energy relaxation of carriers in disordered InxGa1-xAs/GaAs quantum wells
No full text
Formation and relaxation of exciton-carbon acceptor complexes in GaAs
No full textPhotoluminescence excitation (PLE) measurements have been performed in several GaAs-based structures by monitoring the electron-carbon acceptor and the exciton bound to carbon recombinations. In both cases we show that the separate capture of free carriers makes the main contribution to the electron-carbon transition and to the formation of the bound exciton. A dip is indeed observed in the PLE spectra at the energy of the free exciton. The contribution of the bound exciton relaxation to the two-hole transition is pointed out
Excitation Transfer through Thick Barriers in Asymmetric Double Quantum Well Structures
No full textThe transfer of carriers between two adjacent InxGa1−xAs wells with different thicknesses and separated by a thick GaAs barrier has been measured as a function of temperature for different indium concentrations x. The efficiency of the carrier transfer has been determined by photoluminescence excitation measurements. It is roughly constant at low temperature, and increases for increasing temperatures, going through a maximum between 50 and 70 K. At higher temperatures, where the photoluminescence shows a drastic quenching, also the carrier transfer efficiency decreases rapidly. The thermal escape of carriers out of the narrow well mediates the transfer, quenched at higher temperatures by an increased role of nonradiative recombination centres in the well and/or in the barrier. A comparison with a simple rate equation model supports an ambipolar escape of carriers in cw measurements, a unipolar escape of carriers in time-resolved measurements. This is explained in terms of the different excitation conditions in two types of experiments
Eccitoni localizzati in sistemi disordinati: dal materiale massivo ai punti quantici
No full textDottorato di ricerca in scienza dei materiali. 12. ciclo. A.a. 1998-99. Relatore M. Capizzi. Coordinatore A. FurlaniConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal
