Formation of High‐Quality Heteroepitaxial β‐Ga2O3 Films by Crystal Phase Transition

Abstract Sn‐doped ɛ‐phase dominant Ga 2 O 3 films (ɛ‐Ga 2 O 3 films) are grown on c ‐plane sapphire substrates using metal–organic vapor‐phase epitaxy and transformed to β‐phase films by thermal annealing. The morphological and electrical properties of the phase‐transformed β‐Ga 2 O 3 films dependent on experimental conditions are characterized. The ɛ‐Ga 2 O 3 film is completely transformed to the β‐phase by thermal annealing to realize a high electrical conductivity while maintaining a good surface flatness. When the ɛ‐Ga 2 O 3 films are grown, a mixing ratio of the β‐Ga 2 O 3 component to the ɛ‐Ga 2 O 3 film is controlled to improve the crystalline quality of the β‐Ga 2 O 3 films transformed from ɛ‐Ga 2 O 3 by annealing (transformed β‐Ga 2 O 3 ). Compared to an as‐grown β‐Ga 2 O 3 film, higher‐quality heteroepitaxial β‐Ga 2 O 3 films with better electrical conductivity and surface morphology can be obtained by the phase transition method, and these results show adequate repeatability.