Fabrication and Characterization of Mg-Doped GaN Nanowires

Mg-doped GaN nanowires have been synthesized by ammoniating Ga₂O₃ films doped with Mg under flowing ammonia atmosphere at 850°C. The Mg-doped GaN nanowires are characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL). The results demonstrate that the nanowires are single crystalline with hexagonal wurzite structure. The diameters of the nanowires are 20-30nm and the lengths are 50-100μm. The GaN nanowires show three emission bands with well-defined PL peak at 3.45eV, 3.26eV, 2.95eV, respectively. The large distinct blueshift of the bandgap emission can be attributed to the Burstein--Moss effect. The peak at 3.26eV represents the transition from the conduction-band edge to the acceptor level AM (acceptor Mg). The growth mechanism of crystalline GaN nanowires is discussed briefly.