(AlxGa1−x)2O3 is a novel ultra-wide bandgap semiconductor with the potential to dominate future power electronics industries. High-performance devices demand high Al content in (AlxGa1−x)2O3 but are limited by crystallinity degradation resulting from phase separation. Additionally, the solubility limit of Al is still under debate, and conclusive research is in progress. (AlxGa1−x)2O3 is also limited in high-frequency applications owing to low carrier mobility and requires n-type doping. For commercializing this material, the major obstacle is understanding dopant's behavior in the host (AlxGa1−x)2O3. To investigate these issues, an advanced characterization technique, atom probe tomography (APT), was employed to analyze the structural-chemical evolution of (AlxGa1−x)2O3. In this review, we summarized our recent works on the structure-chemistry investigation of (AlxGa1−x)2O3 with alloy composition and doping interaction. We introduced machine learning algorithms on APT data to reveal unrivaled knowledge, previously not achievable with conventional methodologies. The outstanding capabilities of APT to study (AlxGa1−x)2O3 with Al composition and doping will be considered significant for the wide bandgap semiconductors community.