Strain of M-plane GaN epitaxial layer grown on β-LiGaO₂ (100) by plasma-assisted molecular beam epitaxy

We have grown a high-quality single-phase M-plane GaN on β-LiGaO₂ (100) by plasma-assisted molecular beam epitaxy. The Hooke’s law for M-plane GaN was derived by a stress tenor transformation. From the analysis of M-plane GaN microstructure, the lattice strain of M-plane GaN along the [112¯0] and [0001] directions have been estimated. Based on the Hooke’s law, we calculated the ratio of anisotropic stress which was consistent with the ratio of thermal expansion-mismatch between GaN and LiGaO₂ (100). We demonstrated that the thermal expansion mismatch was the major factor to degrade the quality of M-plane GaN on β-LiGaO₂ (100).