Influence of annealing on the thermal quenching of photoluminescence in GaAsBi/GaAs quantum dots with bimodal inhomogeneous broadening

GaAsBi/GaAs quantum dots (QDs) samples with a bimodal size distribution grown by atmospheric pressure metalorganic vapor phase epitaxy (AP-MOVPE) on p-GaAs substrates and annealed at different temperatures were investigated by photoluminescence (PL) measurements. The analyses of the Arrhenius fit of the integrated PL intensity show two types of non-radiative recombination processes, describing the strong thermal quenching of PL. The thermal quenching of the as-grown sample is clearly quicker compared to the annealed QD samples. It is attributed to a higher density of non-radiative Bi complexes and native defects related to GaAs host lattice. The activation energy value for the large QD increases in the annealed samples suggests a modification in the depth of the confining potential. The temperature dependence of the PL peak energy of small QD presents an S-shape variation, while the PL line width follows a non-monotonic form. These behaviors have been progressively reduced in the annealed samples. These experimental results have been interpreted in the context of the thermally activated carrier transfer process between different QDs. Thus, annealing reduces the localized state density and therefore improves the optical quality of GaAsBi/GaAs QDs.