Comparison of Exciton-Biexciton with Bound Exciton-Biexciton Dynamics in GaN: Quantum Beats and Temperature Dependence of the Acoustic-Phonon Interaction

The polarization dependence of biexcitonic signals and quantum beats between A-excitons (X A ) and A-biexcitons (X A X A ) in a high-quality GaN epilayer is measured by spectrally-resolved and time-integrated four-wave mixing. With cross-linear polarised light, mixed beats with two periods are observed: the first beating period corresponds to the energy splitting between X A and X A X A , and agrees well with the calculated X A X A binding energy; while the second beating period corresponds to that between X A and donor bound excitons (D°X). The temperature-dependent homogeneous linewidth shows that the D°X has a larger acoustic phonon coupling coefficient than the X A X A . We also measured the polarization dependent B-biexciton (X B X B ) signal. The effective masses for the A- and B-hole were deduced from the binding energy.