Probing Bond Length and Compositional Disorder in β‐(AlxGa1−x)2O3 Alloys Using Extended X‐Ray Absorption Fine Structure Spectroscopy

Abstract

Local structure of β‐(AlxGa1−x)2O3 alloys with Al contents is determined from extended X‐ray absorption fine structure spectroscopy (EXAFS). A model to fit the EXAFS data for monoclinic β‐(AlxGa1−x)2O3 is suggested to independently determine local structure parameters. An increase in compositional disorder corresponding to the near neighbors (NNs) for lower Al contents establishes that the Al atom does occupy tetrahedron sites in addition octahedron sites even for smaller Al contents. NNs and next‐nearest neighbor (NNN) bond lengths corresponding to tetrahedron and octahedron coordinated gallium (Ga) atoms with surrounding oxygen (O) atoms as well as tetrahedron–tetrahedron/octahedron–octahedron coordinated GaGa atoms on average decrease with Al content up to x = 33.3% and then they saturates with further increase in Al content. However, tetrahedron–octahedron coordinated GaGa atoms move far apart with Al content up to x = 33.3% and then it saturates. The physical picture indicates the creation of tetrahedra and octahedra sublattices locally for β‐(AlxGa1−x)2O3, and their sizes decrease, but they move far apart up to a certain Al content. Thereafter, both saturate. Thus, EXAFS provide a clear insight into the evolution of local structure of β‐(AlxGa1−x)2O3 with Al content, which is useful for better understanding of their physical properties.