Abstarct: III-nitrides are presently of great interest because of the potential for developing from this material system a wide range of optoelectronics devices operating in the blue and ultraviolet portion of the spectrum, as well as electronic devices capable of operating at high frequency, high temperature and high power. Much research interest has focused on three mechanisms affecting III-Nitride device performance: phase-segregation resulting from In clustering in InGaN alloys, piezoelectricity in InGaN resulting from the lattice mismatch between InGaN and the GaN substrate and spontaneous polarization of InGaN resulting from the asymmetry in the tetrahedral sub-structure of the wurtzite lattice. It is of significant technological importance to determine the relative contribution of each of these processes to the emission efficiencies in these nitride materials. The InGaN alloy has a specific behavior that makes it important and complicated. Indium tendency to segregate and form the phase separated medium in the well products the Q.D-like regions in the well. These In-rich clusters play an important role in the optical recombination mechanisms and act as localization centers for capturing the excitons. On the other hand exact value of InN energy gap is under debate. However there are reports which determine its value about 0.7-2.1 eV. Since InGaN is the active region (quantum well) in InGaN/GaN MQWs, it is important to investigate the structural and optical properties of this material. The luminescence characteristics of InGaN quantum well structures were investigated as a function of excitation power and temperature. This thesis represents the characterization of the InGaN/GaN MQWs which were grown on sapphire substrate by mextal-organic chemical vapor deposition (MOCVD) method. The technique used for characterization is photoluminescence (PL). The aim is the optimization of InGaN growth, including finding the best growth temperature comparing different indium content and flow during the growth.