The influence of Ga source and substrate position on the growth of low dimensional GaN wires by chemical vapour deposition

This paper presents the investigation of low dimensional GaN structures synthesized from Ni-catalyzed chemical vapour deposition (CVD) method under two different conditions, i.e. Ga source and substrate position. Comparative studies based on the morphological, structural and optical characteristics of synthesized GaN wires were carried out in this work. The variations of morphological and dimensional aspects of the GaN wires were attributed to the position of Ga precursor and substrates. These factors were found to be able to influence the degree of supersaturation of gaseous reactants, which is essential in the growth of GaN wires by vapour-liquid-solid (VLS) mechanism. The synthesized GaN wires typically were found to have diameters ranging 35-80 nm (nanowires) and 0.4-1.3 μm (microwires), respectively, with length up to several ten of microns. X-ray diffraction (XRD) results indicated that the grown GaN wires were hexagonal wurzite phase. Ultraviolet (UV) and blue emissions were observed from photoluminescence (PL) measurements. Raman spectra displayed asymmetrical and broadened bands which could be ascribed to the size effect, surface disorder and internal strain of the synthesized GaN wires.