Telecom wavelength single quantum dots with very small excitonic fine-structure splitting

We report on molecular beam epitaxy growth of symmetric InAs/InP quantum dots (QDs) emitting at a telecom C-band (1.55 mu m) with an ultra-small excitonic fine-structure splitting of similar to 2 mu eV. The QDs are grown on a distributed Bragg reflector (DBR) and systematically characterized by micro-photoluminescence (mu-PL) measurements. One order of magnitude of QD PL intensity enhancement is observed in comparison to the samples without DBR. A combination of power-dependent and polarization-resolved measurements reveals background-free exciton, biexciton, and dark exciton emission with a resolution-limited linewidth below 35 mu eV and a biexciton binding energy of similar to 1 meV. The results are confirmed by statistical measurements of about 20 QDs. Published by AIP Publishing.