In the last year charged excitons and biexcitons came in the center of interest. I will investigate theoretically the charged excitons and bi-excitons bound to interface defects in shallow quantum wells. They seem to play an important role in the evolution of the optical response of quantum wells for increasing excitation or carrier concentration. The charged exciton for example appears to play a decisive role in doped quantum wells: He holds for varying carrier concentration an intermediate position between the regular exciton and the Coulomb correlated electron-hole-pair.
A further unanswered question is whether the charged excitons and bi-excitons are bound or free. Based on the theoretical results for strongly confined quantum dots I will analyse their binding energies. I plan to study the stability of the charged excitons and bi-excitons in shallow quantum wells by means of variational calculations. My objective is to see if the binding energy is compatible with available experimental findings.