MOCVD Epitaxy of Ultrawide Bandgap β-(AlxGa1-x)2O3 with High-Al Composition on (100) β-Ga2O3 Substrates

Single beta-phase (100) (AlxGa1-x)(2)O-3 thin films were successfully grown on (100) oriented beta-Ga2O3 substrates via metalorganic chemical vapor deposition (MOCVD). By systematically tuning the precursor molar flow rates and growth conditions including chamber pressure, growth temperature and group VI/III molar ratio, pure beta-phase (100) (AlxGa1-x)(2)O-3 films with up to 52% of Al compositions were achieved. Comprehensive material characterization via X-ray diffraction (XRD) and highresolution scanning transmission electron microscopy (HR-STEM) revealed high quality epitaxial growth of (100) beta-(AlxGa1-x)(2)O-3 films on (100) native substrates. High resolution X-ray spectroscopy (XPS) was used for determining the AlGaO bandgaps and the Al compositions. Two-dimensional defects in the beta-(AlxGa1-x)(2)O-3 films were investigated utilizing atomic resolution STEM imaging. Additionally, film characterization via HR-STEM imaging, XRD, and energy-dispersive X-ray spectroscopy (STEM-EDS) revealed coherent growth of high quality (100) beta-(AlxGa1-x)(2)O-3/Ga2O3 superlattice (SL) structures (x = 50%) with abrupt interfaces and relatively uniform Al distribution. Step flow growth of (100) beta-(AlxGa1-x)(2)O-3 with smooth and featureless surface morphology was observed in AlGaO samples with high-Al compositions. A mechanism for the stepflow growth of high-Al content beta-(AlxGa1-x)(2)O-3 film is proposed by considering Al adatoms as preferred incorporation sites for AlGaO nucleation and growth.