Highly Stable White Light Emission from III-Nitride Nanowire LEDs Utilizing Nanostructured Alumina-Doped Mn⁴⁺ and Mg²⁺

Abstract

In this report, red-emitting alumina nanophosphors doped with Mn 4+ and Mg 2+ (Al 2 O 3 :Mn 4+ , Mg 2+ ) are synthesized by a hydrothermal method using a Pluronic surfactant. The prepared samples are ceramic-sintered at various temperatures. X-ray diffraction shows that Al 2 O 3 :Mn 4+ , Mg 2+ annealed at 500 °C exhibits a cubic γ-Al 2 O 3 phase with the space group Fd3m-227. The tetragonal δ-Al 2 O 3 and rhombohedral α-Al 2 O 3 phase is obtained at 1000 and 1300 °C, respectively. Cube-like nanoparticles in a size of ∼40 nm are observed for the alumina heated at 500−1000 °C. The size and red-emitting intensity of the phosphors remarkably increased with annealed temperature ∼1300 °C. Emission spectra of the phosphors show strong peaks at 678 and 692 nm due to 2 E g → 4 A 2 transitions of the Mn 4+ ion, under a light excitation of 460 nm. A strong zero-phonon line (ZPL) emission is observed in the luminescence spectra of δ-Al 2 O 3 :Mn 4+ , Mg 2+ at 298 K, whereas a weak one is observed in those of αand γ-Al 2 O 3 :Mn 4+ , Mg 2+ . The alumina phosphors exhibited an excellent waterproof ability during 60 days in water and good thermal stability in the range of 77−573 K. A warm-white light-emitting diode (WLED) fabricated using In x Ga 1−x N nanowire chips with Al 2 O 3 :Mn 4+ , Mg 2+ red-emitting nanophosphors presents a high color rendering index of ∼95.1 and a low correlated color temperature of ∼4998 K. Moreover, the current−voltage characteristic of the nanowire LEDs could be improved using Al 2 O 3 :Mn 4+ , Mg 2+ nanophosphors which is attributed to the increased heat dissipation in the nanowire LEDs.

Role of Gold Nanoparticles in Gallium Nitride Growth for Potential Plasmonic Device Applications

“…Group III nitrides have been widely used in the development of light-emitting devices because of their high recombination rate, especially in the generation of high-efficiency white emission technologies. − For instance, Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura received the Nobel Prize in physics in 2014 for their contribution to the development of the ultrabright blue light-emitting diode linked to the creation of white light technology. − …”