This paper presents the growth and characterization of metallic gallium three-dimensional (3D) structures and preliminary results of their transformation into GaN-like structures. The structures were grown by metal-organic vapour phase epitaxy (MOVPE), using trimethyl gallium as gallium precursor on silicon (100). The growth temperature was between 550degreesC and 750degreesC. Interesting and new metallic structures were obtained with our growth parameters: balloon (montgolfier-like structure) and cauliflower-like. These metallic structures can grow up perpendicular to the substrate surface and have diameters between 0.1 and 5 mum, depending on the growth conditions. Moreover. selective metallic growth was obtained with our growth conditions. Some discussions about the growth mechanism are also presented. The Ga 3D nitridation process was carried out by annealing under NH3 between 650degreesC and 750degreesC. far below the conventional nitridation temperature in MOVPE. Preliminary X-ray diffraction results show that a GaN-like structure can be obtained at such low nitridation temperature. (C) 2003 Elsevier B.V. All rights reserved.