Dynamics of the bound excitons in GaN epilayers grown by hydride vapor phase epitaxy

We report on time-integrated and time-resolved photoluminescence (PL) measu rements in 80 mu m thick GaN layers grown by hydride vapor phase epitaxy on sapphire substrates. The PL spectra are dominated by Gee exciton transitio ns and by three well-resolved emissions assigned to the neutral-donor-bound exciton and two neutral-acceptor-bound exciton transitions at 3.478, 3.473 and 3.461 eV, respectively. A remarkably long radiative lifetime of 3600 p s was determined for the acceptor-bound exciton with peak position at 3.461 eV. The temperature evolution of the recombination lifetime for the bound excitons suggests that the main nonradiative process is connected with diss ociation of the bound excitons into free excitons, which is in agreement wi th the temperature dependences of the integrated PL intensities measured fo r bound and free exciton transitions.