Tailoring the optical properties of InAs/GaAs quantum dots by means of GaAsSb, InGaAs and InGaAsSb strain reducing layers

Self-organized InAs QDs have been grown by Molecular Beam Epitaxy with different strain reducing layers (SRL) having nearly similar lattice mismatches to GaAs. The used SRLs are GaAsSb, InGaAs and InGaAsSb. Atomic Force Microscopy (AFM), transmission electron microscopy (TEM), high resolution X-ray diffraction (HRXRD), power dependent photoluminescence (PL) from low to room temperature have been employed for the characterization of the grown samples. Our results revealed that the emission wavelength reaches 1.32 μm when the InAs QD are either covered by InGaAs or GaAsSb with a PL spectrum broadening when using GaAsSb. However, the incorporation of only 1% of Sb in the InGaAs SRL extends further the wavelength to 1.37 μm without altering the PL spectrum. For more quantitative analysis of the observed results, the QDs size dependence on the SRL type has been estimated by tuning the theoretical transition energies, obtained by solving the single band effective mass Schrodinger equation for an ellipsoidal QD through changing the dot size to fit the experimental transition energies. Indeed, in addition to the QDs strain reduction, the type of alloy capping layer is found to seriously alter the QD size and aspect ratio and consequently the energy separation between the first and second excited state. However, from the temperature dependence of the PL, the thermionic emission activation energies were found to be close to separation between the ground and first excited state independently of the SRL type.