29 March 2013 Efficient Ga(As)Sb quantum dot emission in AlGaAs by GaAs intermediate layer
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Ga(As)Sb quantum dots (QDs) are epitaxially grown in AlGaAs/GaAs in the Stranski-Krastanov mode. In the recent past we achieved Ga(As)Sb QDs in GaAs with an extremely high dot density of 9.8∙1010 cm-2 by optimization of growth temperature, Sb/Ga flux pressure ratio, and coverage. Additionally, the QD emission wavelength could be chosen precisely with these growth parameters in the range between 876 and 1035 nm. Here we report a photoluminescence (PL) intensity improvement for the case with AlGaAs barriers. Again growth parameters and layer composition are varied. The aluminium content is varied between 0 and 90%. Reflectance anisotropy spectroscopy (RAS) is used as insitu growth control to determine growth rate, layer thickness, and AlGaAs composition. Ga(As)Sb QDs, directly grown in AlxGa1-xAs emit no PL signal, even with a very low x ≈ 0.1. With additional around 10 nm thin GaAs intermediate layers between the Ga(As)Sb QDs and the AlGaAs barriers PL signals are detected. Samples with 4 QD layers and AlxGa1-xAs/GaAs barriers in between are grown. The thickness and composition of the barriers are changed. Depending on these values PL intensity is more than 4 times as high as in the case with simple GaAs barriers. With these results efficient Ga(As)Sb QD lasers are realized, so far only with pure GaAs barriers. Our index-guided broad area lasers operate continuous-wave (cw) @ 90 K, emit optical powers of more than 2∙50 mW and show a differential quantum efficiency of 54% with a threshold current density of 528 A/cm2.
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Thomas Henning Loeber, Thomas Henning Loeber, Johannes Richter, Johannes Richter, Johannes Strassner, Johannes Strassner, Carina Heisel, Carina Heisel, Christina Kimmle, Christina Kimmle, Henning Fouckhardt, Henning Fouckhardt, } "Efficient Ga(As)Sb quantum dot emission in AlGaAs by GaAs intermediate layer", Proc. SPIE 8634, Quantum Dots and Nanostructures: Synthesis, Characterization, and Modeling X, 86340P (29 March 2013); doi: 10.1117/12.2003641; https://doi.org/10.1117/12.2003641

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