GaN films studied by near-field scanning optical microscopy, atomic force microscopy and high resolution X-ray diffraction

Spatially resolved photoluminescence measurements from GaN films were achieved using a near-field scanning optical microscope (NSOM). We have studied GaN films grown by metalorganic vapor phase epitaxy on sapphire substrates. Spatial scans of topography, band-edge and yellow luminescence have been performed with submicron spatial resolution. Spatial variations in the photoluminescence characteristics are clearly observed at the submicron scale. Measurements by atomic force microscopy and high resolution X-ray diffraction were also performed and compared with the NSOM measurements.