Nonuniform defect distribution in GaN thin films examined by cathodoluminescence

Room-temperature cathodoluminescence depth-profiling studies of GaN films g rown 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.