Synthesis and characterization of Zn-doped GaN crystals by simultaneous carbothermal reduction and nitridation of Ga2O3 and ZnO

GaN powders doped with varying amounts of Zn were deposited on silica glass substrates at 1160 °C by reaction for 1 h of NH3 with gaseous Ga2O and Zn. These precursor gases were produced by reaction of C with Ga2O3 and ZnO, respectively, called carbothermal reduction and nitridation (CRN). For comparison, Zn-doped GaN powders were produced at 1160 °C by direct nitridation (DN) of ZnO/Ga2O3 and ZnGa2O4 powders with NH3. Zn-doped GaN single crystals of 1×0.5 mm2 in size were grown in a silica glass crucible by the CRN method. The crystallinity of the GaN powders was determined by X-ray diffraction and their morphology was observed by scanning electron microscopy. The concentrations of O and Zn in the GaN powders were determined by the combustion and inductively coupled plasma methods. In-depth profiles of the O, H, and Zn concentrations in the GaN single crystals were determined by secondary ion mass spectroscopy. Cathodoluminescence (CL) observation of the GaN powders was performed to evaluate their quality. It is revealed that, compared with the powders prepared by DN, Zn-doped GaN powders produced by CRN exhibit very high CL intensities at 460 nm due to the presence of Zn.