Influence of the temperature on the carrier capture into self-assembled InAs/GaAs quantum dots

Photoluminescence (PL) spectroscopy and atomic-force microscopy (AFM) were used to investigate the size evolution of InAs quantum dots on GaAs(001) as a function of the amount of InAs material. Different families of islands were observed in the AFM images and unambiguously identified in the PL spectra, together with the signal of the wetting layer. PL measurements carried out at low and intermediate temperatures showed a thermal carrier redistribution among dots belonging to different families. The physical origin of this behavior is explained in terms of the different temperature dependence of the carrier-capture rate into the quantum dots. At high temperatures, an enhancement of the total PL-integrated intensity of the largest-sized quantum dots was attributed to the increase of diffusivity of the photogenerated carriers inside the wetting layer. (C) 2003 American Institute of Physics.931016279628

Interplay between direct gap renormalization and intervalley scattering in AlxGa1-xAs near the Gamma-X crossover

We report resonant pump and white probe femtosecond spectroscopy in the Al0.42Ga0.58As multivalley semiconductor. For this alloy composition the energy valleys are near the Gamma-X crossover. Our most interesting result refers to the differential transmission below gap which shows carrier induced absorption and a complex dynamics. The data can be modeled if we take into account the dependence of the gap renormalization on the occupation of each conduction band valley. We infer an interplay between direct gap renormalization and the ultrafast redistribution of the photoinjected carriers that follows ultrafast intervalley scattering in the scenario of multiple valleys close in energy in the conduction band. This shows on femtosecond timescale the contribution of the electron exchange interaction to the band gap narrowing in highly excited multivalley semiconductors. (C) 2002 Elsevier Science Ltd. All rights reserved.121418118

Illumination as a tool to investigate the quantum mobility of the two-dimensional electron gas in a Si delta-doped GaAs/In0.15Ga0.85As/GaAs quantum well

A systematic investigation of the transport properties of a GaAs/InGaAs quantum well electronically coupled to a silicon delta-doped layer was carried out as a function of the illumination time of the sample. Shubnikov-de Haas measurements allowed the determination of the quantum mobility of each occupied subband that could be accurately analyzed from the dark condition up to the continuous-illumination regime. The origin of the persistent-photoconductivity effect observed in the sample could be unambiguously determined and was confirmed by self-consistent calculations.65

Effects of soil mechanical treatments combined with bramble and bracken control on the restoration of degraded understory in an ancient beech forest

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Influence of illumination on the quantum mobility of a two-dimensional electron gas in Si delta-doped GaAs/In0.15Ga0.85As quantum wells

A series of GaAs/InGaAs quantum wells with a silicon delta-doped layer in the top barrier was investigated by Shubnikov-de Haas measurements as a function of the illumination time of the samples. During the illumination process strong modifications of the electronic density and the quantum mobility of each occupied subband were observed. Based on self-consistent calculations, the dominant mechanism which caused the changes in the subband quantum mobilities with illumination was elucidated.15212113

PHOTOLUMINESCENCE AND PHOTOREFLECTANCE STUDIES ON DELTA-DOPED IN0.15GA0.85AS/GAAS QUANTUM-WELLS

Experimental and theoretical studies on delta-doped In0.15Ga0.85As/GaAs quantum wells are reported. Photoreflectance (PR) and Photoluminescence (PL) spectra are measured and compared with results of band structure and PL line shape calculations. The dominating structure seen in the PL spectra is related to the delta-doping well. Its line shape is well described by k(parallel to)-non-conserving radiative transitions.15333333

Band-edge modifications due to photogenerated carriers in single p-type delta-doped GaAs layers

The photogenerated carrier-induced band-edge modifications of beryllium single delta-doped GaAs layers com comprising a two-dimensional hole gas (2DHG) were investigated by means of photoluminescence, selective photoluminescence, and photoluminescence excitation spectroscopies. The results show direct evidence for a photoinduced electron confinement effect, which strongly enhances the radiative-recombination probability between electrons and holes of the 2DHG at low temperatures,5974634463