We report on strong excitonic luminescence in wurtzite GaN at 3.309 and 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 different substrates. From detailed photoluminescence investigations we find small thermal activation energies and a very weak electronndash;phonon coupling. The photoluminescence behavior under hydrostatic pressure is indicative of strongly localized defects. These findings are similar to observations of excitons localized at extended defects such as dislocations in IIndash;VI compounds. copy;1995 American Institute of Physics.
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