Al Incorporation up to 99% in Metalorganic Chemical Vapor Deposition-Grown Monoclinic (Al_xGa_1-x)₂O₃ Films Using Trimethylgallium

Growths of monoclinic (AlxGa1-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 mu m h(-1)) of beta-(AlxGa1-x)(2)O-3 thin films on (010), (100), and ((2) over bar 01) beta-Ga2O3 substrates. By systematically tuning the precursor molar flow rates, growth of coherently strained phase pure beta-(AlxGa1-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 (AlxGa1-x)(2)O-3 films with Al contents up to 99, 29, and 16% are achieved on (100), (010), and ((2) over bar 01) beta-Ga2O3 substrates, respectively. Beyond 29% of Al incorporation, the (010) (AlxGa1-x)(2)O-3 films exhibit beta- to gamma-phase segregation. beta-(AlxGa1-x)(2)O-3 films grown on ((2) over bar 01) beta-Ga2O3 show local segregation of Al along (100) plane. Record-high Al incorporations up to 99% in monoclinic (AlxGa1-x)(2)O-3 grown on (100) Ga2O3 are confirmed from XRD, STEM, electron nanodiffraction, and X-ray photoelectron spectroscopy measurements. These results indicate great promises of MOCVD development of beta-(AlxGa1-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.