Excimer Laser Annealing with a Line Beam for Improvement of Structural and Optical Properties of Polycrystalline GaN

Abstract

Polycrystalline gallium nitride (GaN) thin films of thickness 3.0 µm grown on silica glass substrates were annealed by a line beam of a KrF excimer laser under vacuum. The applied laser energy density was in the range of 300–600 mJ/cm2. Photoluminescence (PL) and X-ray diffraction (XRD) measurements have been carried out to investigate the laser annealing effects in polycrystalline GaN films grown on silica glass by metal-organic chemical vapor deposition (MOCVD). The results of the PL spectra revealed that the intensity of the band edge (BE) emission for the GaN on silica glass annealed at a laser energy density of 500 mJ/cm2 was increased by as much as about 1.5 times in comparison with the as-grown GaN. It was found that the full width at half maximum (FWHM) of the XRD for laser annealed GaN film at a high laser energy density, 500 mJ/cm2, with 200 pulses was smaller than that of the as-grown GaN. These results indicate that the structural and optical properties of the poly-GaN layers grown on silica glass substrate are improved by the laser annealing method.