Photoluminescence from GaN nanopowder: The size effect associated with the surface-to-volume ratio GaN particles of different sizes were separated by a sedimentation technique. We find that a correlation exists between the cathodoluminescence ͑CL͒ spectra of the particles and their average sizes. These results imply that the particles contain a substantial fraction of GaN nanocrystallites ͑NCs͒ whose emission is shifted by quantum size effects and whose proportions differ with the overall size of the particle. X-ray photoelectron spectroscopy data combined with ion etching show that the NCs comprising these clusters have a GaN core surrounded by a gallium oxide shell. The results indicate that size-separated GaN particles may be useful CL sources of light for exciting phosphors over a range of UV wavelengths without the need for alloys such as AlGaInN.

Articles you may be interested inIn-situ NC-AFM measurements of high quality AlN(0001) layers grown at low growth rate on 4H-SiC(0001) and Si (111) substrates using ammonia molecular beam epitaxy AIP Advances 5, 067108 (2015); 10.1063/1.4922193 Influence of the AlGaN buffer layer on the biaxial strain of GaN epilayers grown on 6H-SiC (0001) by molecularbeam epitaxy J. Appl. Phys. 97, 013524 (2005); 10.1063/1.1826219 Single-phase growth studies of GaP on Si by solid-source molecular beam epitaxy Reactive molecular-beam epitaxy of GaN layers directly on 6H-SiC(0001) Appl. Phys. Lett. 75, 944 (1999);The low-temperature growth of GaN is required to prevent cracks due to thermal expansion. The lower limit of the temperature of the GaN growth by compound source molecular beam epitaxy ͑CS-MBE͒ was estimated using the results of reflection high-energy electron diffraction and atomic force microscopy. The lower limit of the temperature of GaN growth by CS-MBE was investigated and found to be below 450°C. The lower limit is due to the migration of atoms at the surface and the re-evaporation of excess Ga atoms.

The fabrication of Zn-doped amorphous GaN (a-GaN : Zn) films deposited on glass substrates is reported. The role of Zn in a-GaN films is also discussed with respect to light emission. A bluish photoluminescence peak at around 450 nm was observed from the a-GaN : Zn films at room temperature, which was not observed from the undoped a-GaN films. The emission intensity of a-GaN films was higher than that of undoped a-GaN films. This is due to the improvement of networks in amorphous films upon the introduction of Zn doping. The Zn doping of a-GaN films is effective for the fabrication of high-luminescent a-GaN films with a strong blue-light emission.

Electroluminescent devices (ELDs) were fabricated using GaNO crystallites. The GaNO crystallites were obtained by the oxidation of GaN crystallites before their annealing in vacuum. Although the cathodoluminescence spectra of GaNO crystallites were broad compared with those of GaN crystallites, the spectral intensities of GaNO crystallites are higher than those of GaN crystallites. In the fabrication of lightemission layers in the ELDs, sedimentation with the selection of GaNO crystallite size was performed. The size selection of GaNO crystallites is effective for the realization of thin and uniform emission layers. It leads to the reduction of operating voltage.

The fabrication of UV/blue electroluminescent devices (ELDs) based on GaN nanocrystallites (NCs) is reported. The electroluminescence spectra of GaN NC‐based ELDs included UV spectral regions. Some of the emission energy is higher than that of the GaN band‐gap transition, which is due to the quantum size effect. The chemical bonding in GaN NCs was measured using X‐ray photoelectron spectroscopy (XPS) with Ar ion beam etching (IBE). The results indicate that GaN NCs consist of a GaN core surrounded by an oxide shell. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)