Neutral and charged biexciton-exciton cascade in near-telecom-wavelength quantum dots

We investigate the cascaded emission of photons from low-density InGaAs/GaAs quantum dots grown by metal-organic vapor-phase epitaxy that are intentionally redshifted toward telecommunication wavelengths. We observe multiple radiative cascades within a single quantum dot and attribute these to neutral and charged excited configurations. The corresponding transitions are identified by combining microphotoluminescence and photon correlation measurements. Full-configuration interaction calculations further support the identification of the emission lines and provide additional information about the confinement of electron and hole wave functions. We apply a Monte Carlo simulation to estimate the effective spin scattering rates between excited triplet and singlet ground states of the negatively charged trion. These spin-flip processes directly affect the observed radiative cascade.