Excitonic Complexes

We have already addressed in the first volume of this textbook that the exciton can form complexes like charged excitons (trions) or excitonic molecules—also called biexcitons. They actually are prominent species in many semiconductors at intermediate excitation conditions in particular in structures of reduced dimensions. We start with the discussion of the particle properties of biexcitons, their non-linear optical spectroscopy and their recombination processes in bulk materials. Since trions due not play much of a role in bulk we proceed to trions and biexctions in two-dimensional structures. We close with some basic properties of excitonic complexes in various types of quantum-dot potentials.