InGaN device quality films and their related heterostructures play a critical role in the development of nitride devices. InGaN growth needs to be performed at much lower temperatures than GaN growth, due to the lower dissociation temperature of InN. Furthermore, decomposition of ammonia becomes less efficient with decreasing temperature due to high kinetic barrier for breaking N-H bonds and InGaN growth needs high NH3/TMIn ratio. We investigated the optical and structural properties of InGaN bulk layers and GaN/InGaN MQWs using thermally precracked ion supplied metalorganic chemical vapor deposition (TPISMOCVD) system. The temperature range for this study was 670 -770°C. In a low NH3 flow condition, In metal droplet appeared on the surface on InGaN layer in conventional MOCVD system, but it disappeared in TPIS-MOCVD system. An increasement of In mole fraction in InGaN could be achieved even in low NH3 flow. As the NH3 flow rate and the InGaN growth temperature decreased, In metal droplet was more effectively reduced by ammonia precracking. The quality of InGaN/GaN MQWs was evaluated with high resolution XRD and TEM.