Biexciton binding energy in parabolic GaAs quantum dots

Biexcitons confined in parabolic quantum dots are investigated both experimentally and theoretically. A biexcitonic beat is observed by using time-resolved four-wave mixing in strain-induced GaAs quantum dots formed in the quantum well. The period of the beat is about 1.5 times shorter than that from the quantum well region in the same well. The shortening of the beat period is direct evidence of an increase in the biexciton binding energy in the quantum dots due to the lateral confinement induced by the stressors. Magnetic field dependence of the biexciton binding energy is investigated, and is found to be almost independent of the external magnetic field up to 8 T. A theoretical calculation of the biexciton binding energy is presented to explain the observed magnetic field dependence.