The InGaN films on GaN layers using a thermally pre-cracked ion-supplied metalorganic chemical vapor deposition (TPIS-MOCVD) system were investigated by a high-resolution X-ray diffraction and the thermodynamic analysis was performed for an NH3 pre-heater by using the computational fluid-dynamic simulations. As the flow rates of NH3 increased, the In composition and the thickness of the InGaN films increased, which meant that the relative indium incorporation efficiency was dependent on the NH3 flow rate and affected by the growth rate. In a low NH3 flow condition, indium metal droplets appeared on the surface of the InGaN layer in a conventional MOCVD system and decreased the indium incorporation efficiency of the InGaN films. The thermodynamic model of the ammonia dissociation did not follow equilibrium conditions and adduct-driven species seemed the actual growth precursors in nitride. The catalyst effect of the NH3 pre-heater plays an important role in the mixing region and growing surface, resulting in the higher indium. incorporation and droplet-free surface in a TPIS-MOCVD system. (C) 2002 Elsevier Science B.V. All rights reserved.