SPATIAL-DISTRIBUTION OF THE LUMINESCENCE IN GAN THIN-FILMS

The spatial dependence of the luminescence intensities at the band edg e (364 nm) and at the ''yellow'' defect-band (centered at 560 nm) regi ons for epitaxial GaN films have been studied using cathodoluminescenc e microscopy at room temperature. The films were grown by metalorganic chemical vapor deposition on (0001) sapphire substrates and were not intentionally doped. Significant nonuniformities in the band-to-band a nd in the yellow band emissions were observed. Yellow luminescence in small crystallites appears to originate from extended defects inside t he grains and at low-angle grain boundaries. The size of band-to-band emission sites correlates with low-angle grain sizes observed by trans mission electron microscopy. (C) 1996 American Institute of Physics.