Structural and optical properties of InAs–GaAs quantum dots subjected to high temperature annealing

Abstract

Annealing at higher temperature (700 °C) of structures with two-dimensional and three-dimensional arrays in InAs–GaAs quantum dots (QDs) results in an increase in the size and in a corresponding decrease in the indium composition of the QDs. The change in the In composition is monitored by the contrast pattern in the plan-view transmission electron microscopy (TEM) images viewed under the strong beam imaging conditions. Increase in the size of the QDs is manifested by the plan-view TEM images taken under [001] zone axis illumination as well as by the cross-section TEM images. We show that the dots maintain their geometrical shape upon annealing. Luminescence spectra demonstrate a shift of the QD luminescence peak toward higher energies with an increase in the annealing time (10–60 min) in agreement with the decrease in indium composition revealed in TEM studies. The corresponding decrease in the QD localization energy results in an effective evaporation of carriers from QDs at room temperature, and the intensity of the QD luminescence decreases, and the intensity of the wetting layer and the GaAs matrix luminescence increase with the increase in the annealing time.

Wetting layer states of InAs∕GaAs self-assembled quantum dot structures: Effect of intermixing and capping layer

“…This, however, seems to remain in contradiction to some experimental observations regarding energies of the optical transitions reported by different authors, concerning, for instance, the InAs/ GaAs WL QWs. [9][10][11][12][13][14][15][16] They are very similar in many reports and are usually in satisfactory agreea͒ Author to whom correspondence should be addressed; electronic mail: grzegorz.sek@pwr.wroc.pl ment with the calculations assuming a rectangular well shape and its fractional thickness of about 1.5 monolayer. [17][18][19] In this paper we aim at presenting a more detailed discussion of the optical transitions related to the existence of the wetting layer in the InAs/ GaAs QD structures, for which we use as main experimental tools the transmission electron microscopy ͑TEM͒ to deduce the composition profiles and photoreflectance spectroscopy to study the absorptionlike spectra.…”

“…It explains both the independence of the WL QW transition energies of the growth conditions in the two InAs layers of our structure ͑the one without the InGaAs cap͒ and their almost constant values over a very broad range of different InAs/ GaAs QD structures reported in the literature. [9][10][11][12][13][14][15][16] In Fig. 6, we have summarized how the room temperature data are scattered in the published papers.…”

“…6, we have summarized how the room temperature data are scattered in the published papers. [9][10][11][12][13][14][15][16] It shows indeed that in spite of different growth conditions used in different laboratories, which influence the dot properties ͑e.g., the data concerning the QD ground state transition energy differ significantly in these reports͒, the WL transition energy remains almost constant within a very narrow range. It might be fully explained, thanks to the calculations we made assuming the QW interface intermixing ͑see Fig.…”

InAs Quantum Dots of Engineered Height for Fabrication of Broadband Superluminescent Diodes

“…Tuning the emission properties of QDs assemblies by in-situ annealing after changing the growth kinetics during the capping (Garcia et al, 1998, Wang et al, 2006, or by post-growth annealing under a GaAs (Leon et al, 1996;Kosogov et al, 1996;Babinski et al, 2001) or SiO 2 proximity cap (Malik et al, 1997;Xu et al, 1998;Yang et al, 2007) have been extensively reported. At the National Research Council of Canada (NRC), we have previously reported Fafard et al, 1999) a growth technique, called indium-flush, to control the size and exciton levels of the self-assembled QDs.…”

Effects of annealing on electrical and optical properties of a multilayer InAs/GaAs quantum dots system

“…On the other hand, the structure of the SAQDs can be made uniform by a post-growth annealing. As a matter of fact, the influence of the annealing was reported using the combination of photoluminescence (PL) and transmission electron microscopy [2][3][4][5][6] . Homogeneous samples were shown to occur due to the atomic interdiffusion process between the barriers and the islands (dots) which changes the sizes and the shapes of the dots.…”