Growth mechanism of InGaN quantum dots on GaN was studied during metalorganic vapor phase epitaxy in a temperature range of 600-750 degrees C in a horizontal reactor. Atomic force microscopy and high resolution X-ray diffraction show that InGaN quantum dots on GaN are formed according to the Stranski-Krastanov growth mode. When growth temperature was varied between 600 and 750 degrees C, a 2-3-dimensional growth transition was observed below 650 degrees C due to the increase in indium content. While the layer thickness was varied, similar transitions were observed with critical thicknesses of similar to 2.7 nm and similar to 4 nm at growth temperatures of 625 degrees C (In(0.31)Ga(0.69)N) and 675 degrees C (In(0.22)Ga(0.78)N) respectively. InGaN quantum dots with a density of similar to 10(10) cm(-2), an average diameter of similar to 40 nm and average height of similar to 4 nm were obtained. Reciprocal space maps from the asymmetric (10-15) reflection show that all the InGaN samples are fully strained. Strong green emission at 534 nm was observed from InGaN grown at 675 degrees C. (C) 2011 Elsevier B.V. All rights reserved.