Characterization of M-plane GaN thin film grown on pre-annealing β-LiGaO2 (100) substrate

The M-plane GaN thin films grown on pre-annealing LiGaO2 (100) substrates by plasma-assisted molecular-beam epitaxy have been characterized. The LiGaO2 (100) substrates were annealed in vacuum and in ambient air, respectively. The analyses of X-ray diffraction and Raman scattering measurements indicate that the crystal quality of M-plane GaN thin film grown on air-annealed LiGaO2 (100) substrate is improved and the compressive stress between M-plane GaN and LiGaO2 is reduced as well. The experimental results reveal that the thermal annealing LiGaO2 substrate in air can effectively suppress the formation of lithium-rich surface to grow a high-quality M-plane GaN thin film on LiGaO2 substrate.

► The LiGaO2 (100) substrates were pre-annealed in vacuum and in ambient air.
► LiGaO2(LGO) annealed in vacuum could form a lithium-rich surface.
► The lithium-rich surface increases the lattice-mismatch between GaN and LGO.
► LiGaO2 annealed in ambient air can avoid the formation of lithium-rich surface.
► The compressive stress between GaN and air-annealed LGO was reduced.