Thermally activated carrier transfer and luminescence line shape in self-organized InAs quantum dots

Abstract

We investigated the temperature dependence (10–180 K) of the photoluminescence (PL) emission spectrum of self-organized InAs/GaAs quantum dots grown under different conditions. The temperature dependence of the PL intensity is determined by two thermally activated processes: (i) quenching due to the escape of carriers from the quantum dots and (ii) carrier transfer between dots via wetting layer states. The existence of different dot families is confirmed by the deconvolution of the spectra in gaussian components with full width half maxima of 20–30 meV. The transfer of excitation is responsible for the sigmoidal temperature dependence of the peak energies of undeconvoluted PL bands.

Time-resolved optical characterization of InAs/InGaAs quantum dots emitting at 1.3 μm

“…1͒, implying that the carrier escape time from the QDs is becoming comparable to the interband recombination lifetime. Thermalization between dots was also observed in short-wavelength InAs/ GaAs QDs [10][11][12] and is responsible for reduced lasing linewidth and increased efficiency at high temperatures in QD lasers. 13,14 Figure 3 shows the measured lifetime at the ground state energy as a function of temperature ͑filled dots, left axis͒.…”

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

“…2,6 These models reveal new effects like the competition between band narrowing by thermal escape processes and band broadening due to exciton-phonon interactions, 7,16 or the role of the wetting layer (WL) continuous states as a mediator for carrier diffusion. 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.…”

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

“…4. For all samples, the higher-lying ground state energy level (QD2) is characterized by the so-called "sigmoidal behavior" and the related FWHM (FWHM QD2 ) has a large value at low T (in the 70-110 meV range) that decreases with increasing T. According to the literature, [27][28][29][30] this behavior results from the thermally activated transfer of carriers from higher-lying QD energy levels towards lower-lying ones and is typical of QD ensembles characterized by large size distributions. On the other hand, the lower-lying ground state energy level (QD1) does not show such behavior and the related FWHM (FWHM QD1 ) slightly changes with increasing T. These observations, together with the fact that all the structures have a FWHM QD1 in the 20-30 meV range, suggest that the large-sized QD family has a reduced size dispersion.…”