A novel rare-earth chloride seed was employed as a catalyst for growth of GaN nano- and micro-crystals on c-, a- and r-plane sapphire. The ErCl3 seed on the substrate surface enhanced the growth rate and density of the GaN crystals. Distinctive green photoluminescence was measured, confirming that Er3+ ions were active in the GaN matrix. This technique can be adapted to selectively grow GaN crystals with emission tailored to the particular optical transitions of the rare-earth seed. (C) 2007 Elsevier B.V. All rights reserved.