Multi-exciton states in semiconductor quantum dots

We present a calculation of the electronic structure and optical emission spectra of multiple excitons confined in a semiconductor quantum dot. As the number of electron-hole pairs is increased, the Coulomb interaction leads to a gradual shift of the transition energies to the lower energy side. Further, elastic Coulomb scattering leads to a carrier-density dependent broadening of the optical transitions. The dominant scattering process involves an electron transferring enough energy to a hole to scatter the latter out of the quantum dot into the barrier layer. The same intra-band Auger scattering process also provides a fast channel for relaxation of an electron captured into an excited state of the QD, without any assistance of phonons.