Photoluminescence (PL) measurements were performed on cubic GaN films grown on GaAs(100) substrates by metalorganic vapor phase epitaxy. The cubic GaN films show a high optical quality that enables us to study the PL spectra in detail. From temperature and excitation intensity dependence, the emission lines at 3.274 and at 3.178 eV were assigned to the excitonic transition and the donor–acceptor pair transition, respectively. We also observed two additional emission lines at 3.088 and 3.056 eV. An excitonic emission at 3.216 eV with full width half maximum value as small as 73 meV was observed at 300 K. ©1997 American Institute of Physics.