Structural investigation of GaN powders thermally annealed at various temperatures

Neutron diffraction(ND) has been utilized in this study to investigated the change of structural properties for GaN powders annealed in an NH3 atmosphere at temperatures of 850, 950, 1050 and 1150 .deg. C for 2 hours; GaN powders annealed at 1050 .deg. C in a N2 atmosphere for 2 hours were prepared, for comparison. Scanning electron microscopy(SEM), X-ray diffraction(XRD) and Raman scattering(RS) were performed additionally to help the interpretation of the spectra of the ND. The results of the ND experiments showed that the peaks in the ND spectra of the samples annealed in an NH3 atmosphere became stronger and narrower as annealing temperature increased. It was observed from the ND experiments that the nitrogen-deficient phases such as Ga2O3 and GaO2H were present in the sample annealed at 1050 .deg. C in a N2 atmosphere, but that such nitrogen-deficient phases were absent in the GaN powders annealed in an NH3 atmosphere. Our analysis of the ND data along with the SEM, XRD, and RS result revealed that the surface of the aggregates of the GaN powders annealed in a N2 atmosphere was of N-deficient phases such as Ga2O3 or GaO2H phases