Enhancing optical characteristics of InAs/InGaAsSb quantum dot structures with long-excited state emission at 1.31 μm.

In this study, the optical properties of InAs quantum dots (QDs) with various strain-reducing layers (SRLs) of GaAsSb and InGaAsSb are characterized using photoluminescence (PL) and time-resolved PL (TRPL) measurements. The room-temperature PL results for the InAs/InGaAsSb QDs revealed stronger emission intensities than InAs QDs capped with an GaAs(1-x)Sb(x) (x = 20%)SRL, although both samples were grown under the same Sb flux during the molecular beam epitaxy process. The InAs/InGaAsSb QDs showed a significant elongation of emission wavelengths to 1450 and 1310 nm for the ground and first-excited state at room temperature. The energy band alignment of the InAs QD heterostructures was found tailoring from type II to type I as the GaAsSb SRL was replaced by InGaAsSb layer, which improved the radiative efficiency and was verified by power-dependent PL and TRPL measurements. Post-growth rapid thermal annealing was applied on the InAs/InGaAsSb QDs to further enhance the QD quality and PL emission efficiency. The greatly improved PL intensity, reduced linewidth, shortened radiative lifetime, with increasing annealing temperature were demonstrated, and InAs/InGaAsSb QDs exhibited enhanced optical characteristics for long-wavelength emission applications.