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9 September 2019 Improved carrier confinement and strain profile in heterogeneously coupled SK-SML quantum dot heterostructure
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It is known that heterogeneously coupled dot structure consisting of sub monolayer (SML) and Stranski Krastanov quantum dots (QDs) has less cumulative strain compared to that in the homogeneously coupled SK dots structure which leads to better carrier confinement in the heterogeneously coupled structure. Here we have theoretically analysed the two heterogeneously coupled dot structures having SML series deposited over SK QDs (Samples A, B, C) and SK QDs over the SML stacks (samples D, E, F). Samples A and D have 1 nm, samples B and E have 2 nm, and samples C and F have 3 nm of InGaAs capping layer thickness over the InAs QD. The optimized structure obtained from previous experimental study consists of six SML stacks with barrier thickness of 7.5 nm between SML and SK QDs. The simulated peaks were validated with experimental data for reliability. Our motivation is to compare hydrostatic and biaxial strains and to find the better structure for long wavelength detection along with high-temperature operation conditions. The result shows that magnitude of hydrostatic strain decreases with the capping layer thickness in both systems indicating carrier confinement of samples C and F are better than the others. Therefore, they can be operated at a slightly higher temperature compared to the other samples. Furthermore, in both systems, biaxial strain in the dot has a positive correlation with the capping layer thickness, showing maximum valence band splitting in samples C and F, thus having lower band gap which makes them a better choice for longer wavelength detection.
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Rajkumar RamaVath, Pravin Raut, Jhuma Saha, and Subhananda Chakrabarti "Improved carrier confinement and strain profile in heterogeneously coupled SK-SML quantum dot heterostructure", Proc. SPIE 11085, Low-Dimensional Materials and Devices 2019, 1108516 (9 September 2019);

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