High-excitation photoluminescence in GaN: Hot-carrier effects and the Mott transition

Photoluminescence under intense excitation is studied in GaN. As the excitation density increases, we show the Mott transition between an excitonic recombination to a plasma-type recombination. The carrier density at the Mott transition is given. At and above the Mott density, we show that the carrier temperature is higher than the lattice temperature. The energy relaxation of the hot plasma is shown to be dominated by LO-phonon emission. Coulomb screening and band-gap renormalization are observed from the photoluminescence peak position and the measured renormalization factor is in good agreement with elementary many-body theory. Finally the dependence of the Mott density on carrier temperature is shown to follow a Debye-H\"uckel model.