Crystal growth and characterization of gallium oxynitride nanowires grown on seed crystals

Nanowires of gallium oxynitride with wurtzite type structure were grown using seed crystals obtained by ammonia nitridation of an amorphous gallium oxide precursor containing 3 at% nickel additive. The seed crystals on a silica substrate were annealed with the amorphous gallium oxide precursor under ammonia flow to grow gallium oxynitride nanowires. The nanowires grew to lengths of about 150 μm along the seed crystals parallel to the hexagonal c-plane at 750 and 800℃ but they did not grow in the lateral direction. When the growth temperature was increased above 900℃, the growth direction gradually changed to become parallel with the c-axis with a copresenting of gallium-nitride-like crystals. Room-temperature cathodoluminescence spectra of nanowires grown at 800℃ exhibited strong blue emission at 2.69 eV along with weak band-edge emission at 3.39 eV, similar to GaN. The latter emission was intense for nanowires grown at 1000℃, which had an improved crystallinity and a higher nitride/oxide ion ratio. Nanowires grown at 750 and 900℃ exhibited persistent photoconductivity under UV irradiation at 393 nm