STRONGLY LOCALIZED EXCITONS IN GALLIUM NITRIDE

We report on strong excitonic luminescence in wurtzite GaN at 3.309 an d 3.365 eV (T = 6 K). These lines Lie well below the band gap and are found commonly in layers grown by different techniques and on differen t substrates. From detailed photoluminescence investigations we find s mall thermal activation energies and a very weak electron-phonon coupl ing. The photoluminescence behavior under hydrostatic pressure is indi cative of strongly localized defects. These findings are similar to ob servations of excitons localized at extended defects such as dislocati ons in II-VI compounds. (C) 1995 American Institute of Physics.