Symmetry aspects of exciton–exciton interactions and biexciton transitions in wurtzite semiconductor structures

Abstract

AbstractThe inelastic collision of two excitons or the optical decay of a biexciton can induce a transition into an exciton and a photon. From the symmetry point of view, we have studied the states of free and bound biexcitons in bulk GaN with the wurtzite structure and in GaN/AlN heterostructures. Due to the antisymmetry properties arising from the exchange of identical fermions, the ground state of the free Γ biexcitons involving two holes from the same valence band is totally symmetric with respect to the symmetry group of the structure. We established the optical selection rules as well as the possible channels for the processes mentioned above and showed that, whatever is the symmetry of a biexciton, there are at least two channels for its optical recombination. That suggests fast recombination processes. If one (several) phonon(s) is (are) involved in a process, it is always possible to connect by an optical transition any initial state to any final one. An electric field applied parallel to the growth axis lowers the symmetry of superlattices to that of quantum wells. All the results remain valid for any bulk semiconductor with the wurtzite structure and for any wurtzite‐based heterostructure with identical cations or anions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)