Microscopic and Spectroscopic Investigation of (AlxGa1–X)2O3 Films: Unraveling the Impact of Growth Orientation and Aluminum Content

Abstract (Al x Ga 1–x ) 2 O 3 is an ultrawide‐bandgap semiconductor with a high critical electric field for next‐generation high‐power transistors and deep‐ultraviolet photodetectors. While (010)‐(Al x Ga 1–x ) 2 O 3 films have been studied, the recent availability of (100), (01)‐Ga 2 O 3 substrates have developed interest in (100), (01)‐(Al x Ga 1–x ) 2 O 3 films. In this work, an investigation of microscopic and spectroscopic characteristics of (100), (01), (010)–(Al x Ga 1–x ) 2 O 3 films is conducted. A combination of scanning transmission electron microscopy, atom probe tomography (APT), and first‐principle calculations (DFT) is performed. The findings reveal consistent in‐plane chemical homogeneity in lower aluminum content (x = 0.2) films. However, higher aluminum content (x = 0.5), showed inhomogeneity in (100), (010)–(Al x Ga 1–x ) 2 O 3 films attributed to their spectroscopic properties. The study expanded APT's capabilities to determine Ga─O and Al─O bond lengths by mapping their ion‐pair separations in detector space. The change in ion‐pair separations is consistent with varying orientations, irrespective of aluminum content. DFT also demonstrated a similar trend, concluding that Ga─O and Al─O bonding energy has an inverse relationship with their bond length as crystallographic orientations vary. This systematic study of growth orientation dependence of (Al x Ga 1–x ) 2 O 3 films’ microscopic and spectroscopic properties will guide the development of new (100) and (01)‐(Al x Ga 1–x ) 2 O 3 along with existing (010)–(Al x Ga 1–x ) 2 O 3 films.