Temperature dependent luminescence from quantum dot arrays: phonon-assisted line broadening versus carrier escape-induced narrowing

Abstract

The paper presents a theoretical model describing the temperature dependence of the photoluminescence spectrum of self-ordered quantum dots arrays taking into account excitonphonon interaction and thermal carriers transfer. This model is applied to the photoluminescence behaviour of InAs quantum dots grown on GaAs vicinal substrates. It allows distinguishing between effects caused by the different temperature-induced mechanisms and thus provides information about the physical and electronic structure of the quantum dot arrays.

Observation of band alignment transition in InAs/GaAsSb quantum dots by photoluminescence

“…The higher redshift rate for the sample 1 is attributed to the carrier redistribution caused by thermal energy as temperature increases leading to recombination in larger QD area having higher localization energy, so-called interdot hopping. 15 Nevertheless, this phenomenon may not occur from sample 2, since it exhibits negligible deviations from InAs bulk. Since holes are confined in the GaAsSb layer in sample 2 hole energy states do not vary depending on different QD sizes.…”

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

“…6 Therefore, quantum dot size distributions, carrier capture, relaxation, and re-trapping among QDs of different sizes had to be considered to model correctly the QD recombination dynamics. 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.…”

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.…”