Structural and optical properties of InAs/(In)GaAs/GaAs quantum dots with single-photon emission in the telecom C-band up to 77 K

We present a combined experimental and theoretical study of InAs/InGaAs/GaAs quantum dots capable of single photon emission in the technologically important telecom C-band for temperatures of up to 77 K. The structure and morphology of the dots is investigated by means of atomic force microscopy and transmission electron microscopy. Based on these results, the single-particle transition energies are modeled utilizing an atomistic tight-binding method. These energies are compared to experimental data, thereby explaining the mechanism leading to the emission in the C-band as well as the inhomogeneous broadening resulting from fluctuations of size and concentration of individual quantum dots. Additionally, for a single quantum dot, the corresponding multiexciton transition energies are identified. An analysis of the multiexciton states explains the intensity dependence and activation energies of the ensemble spectra at elevated temperatures. As a result, the alternating behavior of specific single dot transitions at different temperatures can be interpreted. Finally, the preservation of single-photon emission up to liquid-nitrogen temperatures of 77 K is demonstrated.