Biexcitons and dark states in semiconductor microcavities

We analyze the formation of two-dimensional biexcitons and the role of exciton dark states decoupled from the cavity mode in semiconductor microcavities containing a few resonating quantum wells. A general formalism is presented for the treatment of excitons, photon modes and biexcitons in resonating microcavities. Scattering by disorder is also considered. The interface disorder seen by cavity polaritons is shown to be reduced by averaging along the cavity axis. The spectral narrowing of cavity polariton lines is discussed. Results for the biexciton binding energy, radius and damping are discussed in the physically relevant cases. The cavity biexciton photoluminescence spectra are found to be qualitatively different depending on the relative magnitudes of the exciton-cavity detuning, the biexciton binding energy, the exciton-photon coupling and the damping. (C) 1998 Elsevier Science B.V. All rights reserved.