In GaN dots grown by droplet epitaxy using NH3, the relation between growth temperature, and size, density, and degree of nitridation was investigated. As growth temperature increased from 390 to 700 degrees C, both enlargement of dot size and a drop in dot density were observed, which seemed to be caused by both migration and evaporation of Ga atoms. In contrast, post-growth annealing at 700 degrees C under an NH3 atmosphere for the sample grown at 520 degrees C had the effects of remarkably increasing dot density, reducing dot size, and improving nitridation of the grown dots. The mechanism of GaN dot growth by droplet epitaxy using NH3 is discussed, and the effectiveness of the post-growth annealing under an NH3 atmosphere is shown. (c) 2006 Elsevier B.V. All rights reserved.