CATHODOLUMINESCENCE OF GAN FILMS GROWN UNDER GA AND N RICH CONDITIONSBY RADIOFREQUENCY MOLECULAR-BEAM EPITAXY

Cathodoluminescence (CL) topographs were taken at room temperature at 364 nm on undoped GaN films grown by plasma-enhanced molecular beam ep itaxy at various V/III ratios. The CL topographs were compared with sc anning electron microscope (SEM) images. The CL topograph was found to be significantly influenced by the V/III ratio during growth. For GaN films grown at low V/III ratio, spatially nonuniform luminescence int ensity was observed. This nonuniformity in luminescence may be due to the local variation of stoichiometry of GaN induced by Ga microsegrega tion. At nitrogen-rich condition, almost flat surfaces in SEM image we re observed and the uniform intensity of luminescence was obtained by CL topograph. Thus, the nitrogen-rich condition is favourable to get s tructually and optically uniform films.