Optical transitions in cubic GaN grown by metalorganic chemical vapor deposition on GaAs (100) substrate

Photoluminescence measurements have been performed on cubic GaN films with carrier concentration as low as 3 x 10(13) cm(-3). From the temperature and excitation intensity dependence, the emission lines at 3.268, 3.150 and 3. 081 eV were assigned to the excitonic, donor-acceptor pair, and free-to-acc eptor transitions, respectively Additionally, we observed two additional em ission lines at 2.926 and 2.821 eV, and suggested that they belong to donor -acceptor pair transitions. Furthermore, from the temperature dependence of integral intensities, we confirmed that three donor-acceptor pair transiti ons (3.150, 2.926, and 2.821 eV) are from a common shallow donor to three d ifferent accepters. The excitonic emission at 3.216 eV has a full-width-at- half-maximum value of 41 meV at room temperature, which indicates a good op tical quality of our sample.