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

In this paper, we report the growth of M-plane GaN thin films on LiGaO2 (100) substrates pre-annealed in vacuum and in air ambient. The surface of M-plane GaN film grown on the LiGaO2 (100) substrate pre-annealed in air ambient was significantly improved. X-ray diffraction data showed that the M-plane GaN thin film grown on the LiGaO2 (100) substrate pre-annealed in air ambient has better crystal quality than that grown on the LiGaO2 (100) substrate pre-annealed in vacuum. In addition, the strain generated between GaN thin film and LiGaO2 substrate was relaxed when the GaN thin film grew on the LiGaO2 substrate pre-annealed in air ambient. It revealed that the thermal annealing LiGaO2 substrate in air ambient can suppress the formation of lithium-rich surface effectively, and then one can grow a high quality M-plane GaN thin film on the LiGaO2 substrate.

► The LiGaO2 (100) substrates were pre-annealed in vacuum and in air ambient. LiGaO2 annealed in vacuum could form a lithium-rich surface.
► The lithium-rich surface changes the lattice parameter of LiGaO2.
► M-plane GaN grown on the lithium-rich surface leads to the increase of defects. LiGaO2 annealed in air ambient can avoid the formation of lithium-rich surface.