Multi-exciton states in semiconductor quantum dots

We present a calculation of the electronic structure and optical emission s pectra 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. Fur ther, elastic Coulomb scattering leads to a carrier-density dependent broad ening 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 scatte ring process also provides a fast channel for relaxation of an electron cap tured into an excited state of the QD, without any assistance of phonons.