Improving the quality of MOCVD-Grown α-Ga2O3 by introducing an AGO buffer on m-plane sapphire

α-gallium oxide has great potential in the power electronics field due to its high Baliga FOM(BFOM), however, the inferior quality of the epitaxial material limits the development of corresponding applications. This study investigates the morphology and behavior of dislocations in α-Ga₂O₃ films and considerably improves both the surface morphology and crystal quality of the films by inserting an (Al_xGa_1-x)₂O₃ buffer. Results reveal that the dislocations within the buffer lead to an overall tilt (0.5°) of the epitaxial layer relative to the substrate during the relaxation of mismatch stress. Furthermore, high-density screw dislocations propagate to the surface when the film reaches a certain thickness, becoming nucleation sites of β-Ga₂O₃ and formation of hillocks which severely damaged the surface quality of the film. But these hillocks on the buffer layer act as barriers to promote lateral growth of the α-Ga₂O₃ film, making dislocations bend and annihilate. By adjusting the morphology of the buffer, high quality α-Ga₂O₃ film is grown with the full width at half maximum (FWHM) of the (30-30) rocking curve decreased from 0.46° to 0.26°, and the surface roughness is reduced from 15.1 nm to 2.45 nm. This work demonstrates the excellent capability of MOCVD in growing high-quality α-Ga₂O₃ films.