Biexcitons in semiconductor microcavities

In this paper, the present status of the experimental study of the optical properties of biexcitons in semiconductor microcavities is reviewed. In particular, a detailed investigation of a polariton–biexciton transition in a high-quality single quantum well GaAs/AlGaAs microcavity is reported. The binding energy and the coherent dynamics of the biexciton state are measured at low temperature using differential reflectivity and transient four-wave mixing spectroscopy, respectively. It is found that the biexciton binding energy is not strongly influenced by the exciton–photon coupling in the microcavity, even if the vacuum Rabi splitting exceeds the biexciton binding energy. However, the presence of a longitudinal built-in electric field that results in a Stark effect slightly reducing the binding energy compared to the value measured on a reference bare quantum well is experimentally pointed out and compared with calculations. Additionally, the polarization decay of the transition from the crystal ground state to the biexciton is measured and is shown to be larger by approximately a factor of two compared to the value measured on the reference quantum well.