Stokes shift in quantum wells: Trapping versus thermalization

Abstract

Low temperature photoluminescence and photoluminescence excitation mea-

Single-exciton energy shell structure in InAs/GaAs quantum dots

“…For quantum well ͑QW͒ structures, a significant Stokes shift is often interpreted as originating from material nonuniformity where in PL experiments carriers tend to diffuse toward regions of lower band gap, causing the PL emission to be redshifted when compared with PLE. 27 In our case, carrier transfer between QDs via tunneling or thermal excitation or diffusion process could in principle produce a similar effect. However, it has been shown using time-resolved spectroscopy that such carrier transfer does not happen at low temperatures for samples with QD densities below 1 ϫ 10 10 cm −2 .…”

Compositional disorder inGaAs1−xNx:Hinvestigated by photoluminescence

“…36 When the disorder-induced broadening of the excitonic DOS is comparable with the carrier thermal energy, instead, a thermal quasiequilibrium is reached within the exciton population after exciton relaxation. 38,39 At low temperature ͑T =10 K͒ and for laser moderate power densities ͑few W / cm 2 ͒, the thermal energy is small ͑k B T = 0.86 meV͒. Therefore, a quasiequilibrium condition can be reached only in systems with a low degree of disorder.…”

“…Data taken from Ref. 38 and relative to In x Ga 1−x As/ GaAs quantum wells are also shown in Fig. 5 as an example of a random, virtual crystal approximationlike alloy, which behaves according to the thermalization model.…”

“…[36][37][38][39] These processes are investigated here by an analysis of the dependence of the Stokes Shift on the degree of compositional disorder, as measured by the FE linewidth. We already pointed out that the Stokes shift shown in Fig.…”

Above-barrier states inInxGa1−xAs/Worren1, Ozanyan2, Hunderi3 et al. 1998Phys. Rev. BSelf Cite10050View full textAdd to dashboardCite

“…We see from the figure that the difference in the energy position of the 11H peak in PL and PLE, the Stokes shift, is small ͑less than 1 meV͒, which indicates low disorder. 24 In this paper we will concentrate on the PLE spectra only, and no PL spectra will be discussed further. 25 The PLE spectra show several peaks at energies both below and above the GaAs free-exciton line at 1.5153 eV ͑dashed line labeled GaAs FX in the figure͒.…”