Exciton luminescence in In 0.3Ga 0.7As/GaAs quantum well heterostructures (original) (raw)
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Physical Review B, 1988
Sharp line structure associated with both the light-hole free exciton (LHFE) and heavy-hole free exciton (HHFE) in multiple-quantum-well structures of GaAs-AI"Ga& "As in photoluminescence and re6ection spectra has been deconvoluted by using photoluminescence excitation spectroscopy. A correlation is established between particular LHFE fine-structure components and specific HHFE fine-structure components. A model is developed to account for the LHFE and HHFE fine structure in these samples which exploits the nonrandom character of the observed spectra. The physical location of the excitons is demonstrated to be in regions of the well(s) with essentially identical interfacial microstructure. Evidence of difusion from effectively-narrow-well regions to wide-well regions is presented.
Interwell excitons in GaAs/AlGaAs double quantum wells and their collective properties
Journal of Experimental and Theoretical Physics, 2000
Luminescence spectra of interwell excitons in GaAs/AlGaAs double quantum wells with electricfield-tilted bands ( n -i -n ) structures were studied. In these structures the electron and the hole in the interwell exciton are spatially separated between neighboring quantum wells by a narrow AlAs barrier. Under resonant excitation by circularly polarized light the luminescence line of the interwell excitons exhibited appreciable narrowing as their concentration increased and the degree of circular polarization of the photoluminescence increased substantially. Under resonant excitation by linearly polarized light the alignment of the interwell excitons increased as a threshold process with increasing optical pumping. By analyzing time-resolved spectra and the kinetics of the photoluminescence intensity under pulsed excitation it was established that under these conditions the rate of radiative recombination increases substantially. The observed effect occurs at below-critical temperatures and is interpreted in terms of the collective behavior of the interwell excitons. Studies of the luminescence spectra in a magnetic field showed that the collective exciton phase is dielectric and in this phase the interwell excitons retain their individual properties.
Selective exciton formation in thin GaAs-AlGaAs quantum wells
Le Journal de Physique IV, 1993
We have found experimentally, that the exciton luminescence rise times in GaAdAlGaAs quantum wells oscillate as a function of incident laser energies. Guided by Monk-Carlo simulations we interpret these results as the occurrence of selective LO-phonon assisted exciton formation.
Optical investigation of biexcitons and bound excitons in GaAs quantum wells
Physical Review B, 1988
The photoluminescence spectra from a number of high-quality GaAs single-quantum-well samples grown by molecular-beam epitaxy reveal a doublet emission having an energy separation of-1.25 meV. A similar doublet was observed in a sample for which the interrupted growth technique was used. Using excitation-intensity-dependent luminescence and time-resolved spectroscopy,~e will show that the lower-energy components of these doublets have diN'erent origins in di6'erent samples and can be attributed either to biexcitons or to impurity-bound excitons. Using low-temperature photoluminescence (PL) from a number of high-quality GaAs multiple-quantum-well samples grown by molecular-beam epitaxy (MBE), Miller and co-workers'2 first reported a double peak whose splitting was-1 meV. The high-energy peak was attributed to the n 1 heavy-hole-free-exciton transition. Based on the excitation intensity, temperature, and polarization dependencies of the lower-energy peak, they concluded that this transition was due to biexcitons with a binding
Superlattices and Microstructures, 1989
The dynamics of exciton formation and decay are investigated in GaAs-AlxGal_xAS (x < 0.Is) multiquantum well structures under low excitation conditions by transient photoluminescence spectroscopy. The time resolution (10ps) is achieved by using the frequency up-conversion technique. At low temperature (T < 50 K), the luminescence is dominated by localized exciton formation and recombination processes: significant Stokes shifts from the exciton absorption line, long non-exponential rise time (ranging from 200 ps to 600 ps) and short radiative lifetime (from 200 ps to Q00 ps) are observed. At higher temperature (T > 80 K), the luminescence is dominated by free exciton radiative recombination with shorter formation time and much larger exciton lifetime (from 3 ns to 6 ns). We suggest that the exciton may trap efficiently at low temperature on interface defects, the areal density of which can be evaluated in a simple manner.
The Emission Spectra Due To Exciton-Exciton Collisions In Gaas/Algaas Quantum Well System
2012
Optical emission based on excitonic scattering processes becomes important in dense exciton systems in which the average distance between excitons is of the order of a few Bohr radii but still below the exciton screening threshold. The phenomena due to interactions among excited states play significant role in the emission near band edge of the material. The theory of two-exciton collisions for GaAs/AlGaAs quantum well systems is a mild attempt to understand the physics associated with the optical spectra due to excitonic scattering processes in these novel systems. The four typical processes considered give different spectral shape, peak position and temperature dependence of the emission spectra. We have used the theory of scattering together with the second order perturbation theory to derive the radiative power spontaneously emitted at an energy ħω by these processes. The results arrived at are purely qualitative in nature. The intensity of emitted light in quantum well systems ...
Extended Abstracts of the 1993 International Conference on Solid State Devices and Materials, 1993
We present the detailed analyses of temporal profiles of photoluminescence from heavy-hole excitons in AlGaAs/GaAs quantum wells. We have observed the two-component exponential decay when the excitation density is low. We have confirmed by measuring the lateral spatial motion of excitons that the fast component is attributed to radiative recombinations of free excitons while the slowly decaying component is due to localized excitons. To the best of our knowledge, this is the first direct observation of localization of 2-dimensional excitons in quantum wells.
Collective behavior of interwell excitons in GaAs/AlGaAs double quantum wells
Journal of Experimental and Theoretical Physics Letters, 2000
Photoluminescence spectra of interwell excitons in double GaAs/AlGaAs quantum wells ( n -i -n structures) have been investigated (an interwell exciton in these systems is an electron-hole pair spatially separated by a narrow AlAs barrier). Under resonance excitation by circularly polarized light, the luminescence line of interwell excitons exhibits a significant narrowing and a drastic increase in the degree of circular polarization of photoluminescence with increasing exciton concentration. It is found that the radiative recombination rate significantly increases under these conditions. This phenomenon is observed at temperatures lower than the critical point and can be interpreted in terms of the collective behavior of interwell excitons.
Temperature Dependence of Exciton Lifetimes in GaAs/AlGaAs Quantum Well Structures
Europhysics Letters (EPL), 1990
We report on continuous-wave and time-resolved measurements of the photoluminescence of goodquality single quantum wells at low temperatures (4-30 K). Luminescence arising from both free and localized excitons is observed and the inhuence of excitation localization on the photoluminescence decay time is investigated. Resonant pumping at the light-hole exciton transition is found to greatly increase the generation of free heavy-hole excitons. In this case, the free-exciton lifetime increases linearly with temperature (10-30 K) and the dependence of the slope on the well thickness is found to be in good quantitative agreement with the theoretical model of Andreani et al. [Solid State Commun. 77, 641 (1991)].