Some aspects of exciton thermal exchange in InAs quantum dots coupled with InGaAs/GaAs quantum wells

Abstract

Photoluminescence (PL), its temperature and excitation power dependences, and PL excitation spectra have been investigated in InAs quantum dots (QDs) embedded in In0.15Ga0.85As/GaAs quantum wells (QWs) as a function of QD density. The QD density varied from 1.1×1011 down to 1.3×1010 cm−2 with the increase in QD growth temperature at the molecular beam epitaxy processing. A set of rate equations for exciton dynamics (relaxation into QWs and QDs, and thermal escape) has been solved to analyze the mechanism of PL thermal quenching in studied structures. Three stages have been revealed in thermal decay of the PL intensity of InAs QDs. Presented mathematical analysis provides the explanations of the mechanism of PL thermal decay as well as the peculiarities of PL excitation power dependences and PL excitation spectra. A variety of activation energies of PL thermal decay and the localization of nonradiative defects in InGaAs/GaAs QW structures with different InAs QD density are discussed as well.

Size dependent carrier thermal escape and transfer in bimodally distributed self assembled InAs/GaAs quantum dots

“…10 Lobo et al 7 found that the efficiency on carrier transfer is limited by the rate of carrier transfer on the WL only for low density samples, and normal Arrhenius dependence has been found for high density samples. A similar result by Zhou et al 19 concluded that the WL might act as a quenching (transfer) channel for low (high) density samples while Torchynska 23 has reported that the effective thermal activation energy might depend on the QD density.…”

“…[23][24][25][26] Thermal escape can be also investigated attending to the nature of the particles being promoted to a higher energy state. 14 Depending on the model, the correlated (excitonic escape), 6,8,10,12,23 the uncorrelated electron-hole pair (ambipolar escape), 4,9,14 or just one of the carriers (unipolar escape) 15 can be considered. Whether one or the other is appropriate in a particular sample depends on the barrier height and therefore might vary for QDs of given composition but different size.…”

“…4,6,8,9,11,[17][18][19][20] The thermally activated escape mechanism initiates the temperature dynamics and therefore has deserved a lot of attention in the past. It has been investigated attending to the available final states, i.e., QD excited states, 15,21 wetting layer, 4,6,7,13,20,22 GaAs barrier, 8,9,23 and impurity/defect levels. [23][24][25][26] Thermal escape can be also investigated attending to the nature of the particles being promoted to a higher energy state.…”

“…It has been investigated attending to the available final states, i.e., QD excited states, 15,21 wetting layer, 4,6,7,13,20,22 GaAs barrier, 8,9,23 and impurity/defect levels. [23][24][25][26] Thermal escape can be also investigated attending to the nature of the particles being promoted to a higher energy state. 14 Depending on the model, the correlated (excitonic escape), 6,8,10,12,23 the uncorrelated electron-hole pair (ambipolar escape), 4,9,14 or just one of the carriers (unipolar escape) 15 can be considered.…”

The effect of high-In content capping layers on low-density bimodal-sized InAs quantum dots

“…[1][2][3] InAs/GaAs structures with a few QDs/lm 2 and emission at 1.3 lm have been successfully prepared by using epitaxial growth conditions that result in large cation migration length [4][5][6] and by growing pseudomorphic InGaAs upper confining layer (UCL) on top of the QDs. 6,7 A complete picture of QD properties in this type of structures is necessary in order to correctly describe carrier dynamics that strongly depends on peculiar characteristics of the structures such as the energy of excited states and wetting layer (WL), 8 the presence of defects and non-radiative recombination centers 9,10 and also the existence of bimodal QD size distributions. 11 The results of this work, concerning the use of high lattice-mismatched UCL, are of interest also for the realization of structures that employ complex capping layers to engineer the properties of QDs, such as infrared photodetectors 12 and QDs in a well structures.…”