Al Incorporation up to 99% in Metalorganic Chemical Vapor Deposition‐Grown Monoclinic (AlxGa1–x)2O3 Films Using Trimethylgallium

Growths of monoclinic (Al x Ga 1− x ) 2 O 3 thin films up to 99% Al contents are demonstrated via metalorganic chemical vapor deposition (MOCVD) using trimethylgallium (TMGa) as the Ga precursor. The utilization of TMGa, rather than triethylgallium, enables a significant improvement of the growth rates (>2.5 μm h −1 ) of β‐(Al x Ga 1− x ) 2 O 3 thin films on (010), (100), and (01) β‐Ga 2 O 3 substrates. By systematically tuning the precursor molar flow rates, growth of coherently strained phase pure β‐(Al x Ga 1− x ) 2 O 3 films is demonstrated by comprehensive material characterizations via high‐resolution X‐ray diffraction (XRD) and atomic‐resolution scanning transmission electron microscopy (STEM) imaging. Monoclinic (Al x Ga 1− x ) 2 O 3 films with Al contents up to 99, 29, and 16% are achieved on (100), (010), and (01) β‐Ga 2 O 3 substrates, respectively. Beyond 29% of Al incorporation, the (010) (Al x Ga 1− x ) 2 O 3 films exhibit β‐ to γ‐phase segregation. β‐(Al x Ga 1− x ) 2 O 3 films grown on (01) β‐Ga 2 O 3 show local segregation of Al along (100) plane. Record‐high Al incorporations up to 99% in monoclinic (Al x Ga 1− x ) 2 O 3 grown on (100) Ga 2 O 3 are confirmed from XRD, STEM, electron nanodiffraction, and X‐ray photoelectron spectroscopy measurements. These results indicate great promises of MOCVD development of β‐(Al x Ga 1− x ) 2 O 3 films and heterostructures with high Al content and growth rates using TMGa for next‐generation high‐power and high‐frequency electronic devices.