Orientation-dependent strain and dislocation in HVPE-grown <bold>α</bold>-Ga2O3 epilayers on sapphire substrates

Orientation-dependent substrates provide effective platforms for achieving alpha-Ga2O3 with low dislocation densities, whereas the associated strain and dislocation dynamics have not been fully explored. Herein, we investigated the evolution of growth mode, interfacial strain, and dislocation propagation in the alpha-Ga2O3 epitaxial layer with various orientations, grown by the halide vapor-phase epitaxy. Strain tensor theory and geometric phase analysis indicate that the m-plane alpha-Ga2O3 epitaxial layer exhibits the lowest misfit tensile strain, measured at epsilon(xx) = 1.46% and epsilon(yy) = 1.81%, resulting in the lowest edge dislocation density. The m-plane lattice exhibits an inclination of 33.60 degrees, while the c-plane lattice is horizontally aligned and the a-plane lattice oriented perpendicularly. The orientation-dependent growth significantly influences stress relaxation through the generation of misfit dislocations, originating from either basal or prismatic slip. Edge dislocations, induced by misfit dislocations, favor the c-axis, remaining well confined within the in-plane interfacial layer of the m-plane alpha-Ga2O3, leading to reduced low edge dislocation density in the subsequent thick epitaxial layer. These findings shed light on the epitaxial dynamics of alpha-Ga2O3 heteroepitaxy, paving the way for the development of high-performance power devices.