Optically induced carrier dynamics was investigated in highly excited m-plane GaN films grown by metalorganic vapor phase epitaxy (MOVPE) on LiAlO2 substrates and compared to a c-plane GaN reference. Photoluminescence (PL) spectra showing spontaneous and stimulated emission (SE) were investigated at room temperature in both backscattering and lateral geometries, the latter using two different orientations of the excitation stripe with respect to the m-plane GaN c-axis. A lower SE threshold was observed for the m-plane GaN film, which may be attributed to a different defect structure and in-plane strain. The threshold in the m-plane GaN layer is the lowest when using stripe excitation along [0 0 0 1], which is caused by a structural anisotropy in the film. The maximum degree of polarization for SE and spontaneous emission in the m-plane GaN film was found to be 0.47 and 0.23, respectively. The light-induced transient grating technique (LITG) provides carrier lifetimes of 40 and 380 Ps for the m-plane and c-plane orientation, respectively, and reveals SE threshold values comparable to the ones obtained by PL. (C) 2011 Elsevier B.V. All rights reserved.