A systematic study of the crystallographic and electrical/optical properties of MOVPE-grown InN was performed, and the factors that restrict the quality of MOVPE InN were elucidated. The quality of grown InN is highly dependant on the thermal decomposition of NH3 as a nitrogen source. At a lower growth temperature (similar to 550 degrees C) a shortage of active nitrogen, due to a lower decomposition rate of NH3, causes the formation of N vacancies in the grown InN. With increasing growth temperature, a more stoichiometric crystal is grown and the electrical/optical properties improve. At temperatures above 600 degrees C, however, deterioration occurs at the N-face of In-polar InN near the substrate interface. This deterioration results in the formation of a porous layer during high temperature (similar to 650 degrees C) growth. There are a few evidences that show that the hydrogen produced by NH3 decomposition causes this degradation. Thus, improving the quality of MOVPE-grown InN by changing the growth temperature can be difficult. However, a short growth time at a high growth rate and a relatively high temperature is one effective way to solve this dilemma, and one can achieve carrier concentrations as low as 4 x 10(18) cm(-3) by growth at 650 degrees C for 30 min. (C) 2009 Elsevier B.V. All rights reserved.