Influence of substrate atomic symmetry on the epitaxy and rotational domain formation of κ-Ga2O3

Abstract

This study systematically explores the structural factors influencing κ-phase gallium oxide (κ-Ga₂O₃) thin film growth and domain formation on non-basal plane substrates. Accordingly, we grew κ-Ga₂O₃ thin films using mist chemical vapor deposition on both basal and non-basal plane sapphire (c-, a-, m-, and r-plane) and GaN (c- and m-plane) substrates for analysis. Crystallinity, orientation, and domain structures were assessed by X-ray diffraction including 2θ–ω scans, rocking curves, and φ-scans. On c- and a-plane sapphire and GaN substrates, κ-Ga₂O₃ with c-axis orientation was selectively stabilized, whereas α-Ga₂O₃ predominantly formed on r- and m-plane sapphire. Regardless of substrate symmetry, all κ-Ga₂O₃ films exhibited persistent three-fold rotational domains, highlighting the limitations of current substrate configurations. These results demonstrate the significant influence of substrate atomic arrangement on phase stability and domain control, emphasizing the need for advanced substrate engineering to realize single-domain κ-Ga₂O₃ thin films with improved crystalline quality.