In this work ,Al0.6Ga0.4N films grown on AlN/sapphire templates by metalorganic chemical va-por deposition (MOCVD) system were characterized by high resolution XRD and low temperature cath-odoluminescence (CL ) methods .It’s found that there exists phase separation phenomenon in the films by XRD measurements .The optical properties obtained from CL spectra confirmed this phenomenon further . The generation of phase separation is attributed to stress relaxation in thick films and the low surface mob-ility of Al atoms .
