Experimental and theoretical study of thermally activated carrier transfer in InAs/GaAs multilayer quantum dots

• Published in: Applied physics. A, Materials science & processing Vol. 126; no. 7
• Main Authors: Abiedh, K., Zaaboub, Z., Hassen, F., David, T., Sfaxi, L., Maaref, H.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.07.2020; Springer Nature B.V
• Subjects: Activation energy; Applied physics; Characterization and Evaluation of Materials; Condensed Matter Physics; Emission; Holes (electron deficiencies); Machines; Manufacturing; Materials science; Multilayers; Nanotechnology; Optical and Electronic Materials; Photoluminescence; Photovoltaic cells; Physics; Physics and Astronomy; Processes; Quantum dots; Solar cells; Surfaces and Interfaces; Temperature; Temperature dependence; Thin Films; Wave functions; Wetting; Bimodal size; Localized carriers; Quantum dots; Decay time; Photoluminescence
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-020-03654-8

In this paper, we have investigated the thermally activated carriers transfer mechanism in closely stacked InAs/GaAs quantum dots (QDs) by means of steady-state photoluminescence (PL) and time-resolved photoluminescence measurements. The 10 K PL spectrum exhibits double-emission peaks where the excitation power dependence reveals that these emission peaks are attributed to large and small QD groups. With increasing the sample temperature, an abnormal line-width shrinkage of large QDs (LQDs) is observed. The increase in PL decay lifetime of LQDs versus temperature is nicely explained as the electron and hole wave function overlap between dot layers induced by vertical electronic coupling effect. Using a thermal escape model, the activation energies for PL thermal quenching at high temperatures (above 80K) were derived from fitting the temperature-dependent PL decay lifetime data of LQDs and SQDs. The determined activation energies show that the escape of electron-hole pairs from QDs occurs via transfer channel located below the wetting layer. These results are well reproduced by a rate equation-based model treating the QDs as a localized-state ensemble. Our results emphasize the important role of the vertically stacked InAs/GaAs QDs structures with thin GaAs spacer layer to slow down the carrier PL decay lifetime of the thermal transfer process between QDs. This finding is important for the use of such structures as intermediate band in solar cells.