M-plane GaN thin films have been grown on beta-LiGaO2 (100) substrates by plasma-assisted molecular-beam epitaxy. Pure M-plane GaN crystal films have been verified by the measurements of X-ray diffraction, micro-Raman scattering, polarization-dependent photoluminescence and atomic force microscopy. The measurements of X-ray diffraction and micro-Raman scattering exhibited the evidences of large compressive stress on the M-plane GaN thin films. Based on experimental results, we showed that the large compressive stress is the major source leading to the peeling of M-plane GaN thin film off substrate after thermal recycles. (C) 2011 Elsevier B.V. All rights reserved.