Search results for "Exciton"
showing 10 items of 317 documents
Consequences of the spatial localization on the exciton recombination dynamics in InGaP/GaAs heterostructures
2002
5 páginas, 4 figuras.
Photoluminescence in silicon-doped n-indium selenide
1994
Photoluminescence results on silicon-doped indium selenide are reported. The effect of temperature and excitation intensity is studied. At low temperature, free and neutral donor bound exciton peaks are observed. Above 100 K only free exciton and band-to-band photoluminescence is detected. In order to give account of the full lineshape as a function of the absorption coefficient, the Urbach absorption tail of InSe is measured. Transmission and reflection photoluminescence spectra are also compared in order to study the effect of carrier diffusion. The shape of the photoluminescence spectrum can be accounted for through a direct gap model.
Type II narrow double barrier quantum well structures : Γ-X coupling and interface effects
1993
Photoluminescence (PL), PL excitation and time resolved PL experiments have been performed on Al0.42Ga0.58As/AlAs/GaAs symmetric double barrier quantum wells (DBQW) with only one or two AlAs monolayers constituting the intermediate barriers. In agreement with the envelope function predictions we show that such DBQW's undergo a type I - type II transition when the GaAs thickness is reduced below 7 and 5 monolayers for 2 and 1 AlAs molecular planes respectively. In type II configuration the PL decay time is found to be strongly dependent on the energy difference between AlAs Xz - and GaAs Γ - electron confined states and the coupling parameter of the Γ and Xz valleys can be deduced (4.2 meV o…
Different temperature renormalizations for heavy and light-hole states of monolayer-thick heterostructures
2000
Abstract We have found that the energy splitting between peaks in the linearly polarized emission from the cleaved surface of an InAs/GaAs monolayer structure triples with increasing temperature in the range from 5 to 150 K. For each polarization the main emission line corresponds to the radiative recombination of either heavy or light-hole excitons bound to the monolayer. The striking temperature behavior of the peak energies originates from the different hole–phonon coupling due to the much larger penetration of the light-hole envelope function into the GaAs. We prove this assertion by confining the light holes to the InAs plane with a strong magnetic field, which leads to a reduction of …
Exciton recombination in self-assembled InAs/GaAs small quantum dots under an external electric field
2002
5 páginas, 3 figuras.-- PACS: 73.63.Kv; 78.55.Cr; 78.67.Hc; S7.12.-- Trabajo presentado en la 7th International Conference on Optics and Excitons in Confined Systems (OECS7).
Optical transitions and excitonic recombination in InAs/InP self-assembled quantum wires
2001
InAs self-assembled quantum wire structures have been grown on InP substrates and studied by means of photoluminescence and polarized-light absorption measurements. According to our calculations, the observed optical transitions in each sample are consistent with wires of different heights, namely from 6 to 13 monolayers. The nonradiative mechanism limiting the emission intensity at room temperature is related to thermal escape of carriers out of the wires.
Recombination processes in unintentionally doped GaTe single crystals
2002
Emission spectra of GaTe single crystals in the range of 1.90–1.38 eV have been analyzed at different temperatures and excitation intensities by photoluminescence, photoluminescence excitation, and selective photoluminescence. A decrease in band gap energy with an increase in temperature was obtained from the redshift of the free exciton recombination peak. The energy of longitudinal optical phonons was found to be 14±1 meV. A value of 1.796±0.001 eV for the band gap at 10 K was determined, and the bound exciton energy was found to be 18±0.3 meV. The activation energy of the thermal quenching of the main recombination peaks and of the ones relating to the ionization energy of impurities and…
Origin of the Enhanced Photoluminescence Quantum Yield in MAPbBr 3 Perovskite with Reduced Crystal Size
2018
Methylammonium lead bromide perovskite (MAPbBr3) has been widely investigated for applications in visible perovskite light-emitting diodes (LEDs). Fine-tuning of the morphology and of the crystal size, from the microscale down to the quantum confinement regime, has been used to increase the photoluminescence quantum yield (PLQY). However, the physical processes underlying the PL emission of this perovskite remain unclear. Here, we elucidate the origin of the PL emission of polycrystalline MAPbBr3 thin films by different spectroscopic techniques. We estimate the exciton binding energy, the reduced exciton effective mass, and the trap density. Moreover, we confirm the coexistence of free carr…
Optical properties of thin films of ZnO prepared by pulsed laser deposition
2004
In this paper we report on the structural features and optical properties of wurtzite ZnO films epitaxially grown on sapphire, fluorite and mica substrates by means of pulsed laser deposition (PLD). Post-deposition annealing results in a clear improvement of the film quality, reflected by the small width of the exciton-related lines in both the absorption and the photoluminescence spectra. Photoluminescence spectra revealed a multi-line structure which is identified in term of free excitons and excitons complexes with neutral donors and deep centers. The relative intensity of the PL lines mainly depends on the nature of the substrate used. Concerning optoelectronic applications it is especi…
Near band edge recombination mechanisms in GaTe
2003
GaTe samples of p-type have been investigated by analyzing the photoluminescence (PL) response for different excitation intensities at energies higher than the band gap. The PL intensity variation of recombination peaks as a function of the excitation intensity has been measured and fitted by a power law. The results show some particular features that do not appear in other III-V and II-VI compound semiconductors. These features can be interpreted by means of the recombination dynamics of the carriers in the band-gap edges. The expressions for the coefficients associated with different recombination rates and the relations between them are derived and used for understanding the recombinatio…