The Raman spectra of unintentionally doped gallium nitride (GaN) and Mg-doped GaN films were investigated and compared at room temperature and low temperature. The differences of E2 and A1(LO) mode in two samples are discussed. Stress relaxation is observed in Mg-doped GaN, and it is suggested that Mg-induced misfit dislocation and electron–phonon interaction are the possible origins. A peak at 247 cm?1 is observed in both the Raman spectra of GaN and Mg-doped GaN. Temperature-dependent Raman scattering experiment of Mgdoped GaN shows the frequency and intensity changes of this peak with temperature. This peak is attributed to the defect-induced vibrational mode.
