Nonuniform defect distribution in GaN thin films examined by cathodoluminescence

Room-temperature cathodoluminescence depth-profiling studies of GaN films grown on sapphire and on SiC are reported. The spectral characteristics were quantitatively analysed taking into account reabsorption effects. We show that whereas GaN films grown on sapphire show a uniform defect distribution, in GaN grown on SiC the defect density is clearly nonuniform and new, low-energy lines appear in emission from deeper layers in the film.