Photoluminescence investigation of GaN films grown by metalorganic chemical vapor deposition on (100) GaAs

GaN films were grown on (100) GaAs substrates by metalorganic chemical vapor deposition and were found to be of (200) cubic or (111) cubic/(0002) hexagonal phase. Their photoluminescence characteristics remained invariant with material phase. We report assignment of band-edge photoluminescence near 3.36 eV and 3.15–3.31 eV in apparently cubic GaN to intrinsic/bound excitons and phonon-assisted, donor-acceptor pair recombination respectively, on the basis of observed temperature and intensity dependences. A free exciton energy of 3.375 eV is deduced at 6.5 K.