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Mn-doped GaN epitaxial films were grown by metal organic chemical vapour deposition (MOCVD).Microstructural properties of films are investigated using Raman scattering.It is found that with increasing Mn-dopants levels,longitudinal optical phonon mode A1 (LO) of films is broadened and shifted towards lower frequency.This phenomenon possibly derives from the difference in bonding strength between Ga-N pairs and Mn-N pairs in host lattice.In addition,optical properties of films are investigated using cathodoluminescence and absorption spectroscopy.Mn-related both emission band around 3.0eV and absorption bands around 1.5 and 2.95eV are observed.By studies on structural and optical properties of Mn-doped GaN,we find that Mn ions substitute for Ga sites in host lattice.However,caxrier-mediated ferromagnetic exchange seems unlikely due to deep levels of Mn acceptors.