Abstract
In this work, we investigate the optical properties of InAs quantum dots (QDs) capped with composite In0.15Al0.85As/GaAs0.85Sb0.15 strain-reducing layers (SRLs) by means of high-resolution X-ray diffraction (HRXRD) and photoluminescence (PL) spectroscopy at 77 K. Thin In0.15Al0.85As layers with thickness t = 20 Å, 40 Å, and 60 Å were inserted between the QDs and a 60-Å-thick GaAs0.85Sb0.15 layer. The type II emissions observed for GaAs0.85Sb0.15-capped InAs QDs were suppressed by the insertion of the In0.15Al0.85As interlayer. Moreover, the emission wavelength was blueshifted for t = 20 Å and redshifted for t ≥ 40 Å resulting from the increased confinement potential and increased strain, respectively. The ground state and excited state energy separation is increased reaching 106 meV for t = 60 Å compared to 64 meV for the QDs capped with only GaAsSb SRL. In addition, the use of the In0.15Al0.85As layers narrows significantly the QD spectral linewidth from 52 to 35 meV for the samples with 40- and 60-Å-thick In0.15Al0.85As interlayers.
Highlights
In the last decades, self-organized quantum dots (QDs) synthesized using the Stranski–Krastanov technique have attracted a great deal of attention
These values were used in samples B, C, and D to find the In content and the thickness of the InAlAs interlayer
InAs QDs capped with composite In0.15Al0.85As/ GaAs0.85Sb0.15 Strainreducing layers (SRLs) with varying In0.15Al0.85As thicknesses were grown and characterized
Summary
Self-organized quantum dots (QDs) synthesized using the Stranski–Krastanov technique have attracted a great deal of attention. Their optical and electronic properties have been investigated intensively owing to their potential applications in optoelectronic devices [1]. During the growth of these nanostructures, significant change in the size and the shape of the QDs occurs during the capping process This process is quite complex and involves intermixing, segregation, or strain-enhanced diffusion [2]. The use of a pure GaAs capping layer limits the QD emission to less than 1300 nm To alleviate this issue, strain-reducing layers made of (Ga, In)(As, Sb, N) have been used [2–7]. The ternary GaAsSb has received particular attention as its resulting band alignment can be tailored to be of type I or
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