Characterization of $M$-plane GaN film grown on $\beta $-LiGaO$_{2}$ (100) by plasma-assisted molecular beam epitaxy

Lithium gallate (LiGaO$_{2})$ has an orthorhombic crystal structure that can be described as a wurtzite-like structure. The\textbf{\textit{ M}}-plane basis of GaN wurtzite structure is nearly matched to the selected lattice axes of pseudo-hexagonal LiGaO$_{2}$. \textbf{\textit{M}}-plane GaN thin films have been grown on $\beta $-LiGaO$_{2}$ (100) substrates by plasma-assisted molecular-beam epitaxy in our group. Pure \textbf{\textit{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 \textbf{\textit{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 \textbf{\textit{M}}-plane GaN thin film off substrate after thermal recycles.