The preparation and characterisation of gallium nitride using the Hi-Prexxfacility

Several previously reported methods have been investigated for the producti on of bulk, high quality, gallium nitride powder. Two principal attempts ar e reported, using solid state metathesis reactions and high temperature flo wing ammonia techniques. Using the latter method high purity, single-phase bulk, wurtzite gallium nitride powder was produced using a very simple meth od. Using the on-lint Hi-Prexx facility the powders have been examined up t o pressures of 41 GPa using EXAFS, X-ray diffraction and photoluminescence along with further SEM analysis. X-ray diffraction showed the powder to be highly pure P6(3)mc (186) wurtzite GaN. PL studies found that there is an a pproximate shift with pressure of 30-37 meV/GPa and with Ga k-edge EXAFS da ta display a clear pressure dependency of the local structure of nearest ne ighbour atoms. (C) 2001 Elsevier Science B.V. AII rights reserved.