Unraveling evolution of microstructural domains in the heteroepitaxy of -Ga₂O₃ on sapphire

Addressing microstructural domain disorders within epitaxial beta-Ga2O3 is critical for phase engineering and property improvement, whereas the associated evolution of beta-Ga2O3 heteroepitaxial domains remains largely unexplored. In this Letter, we conducted a quantitative investigation of microstructural domains in (-201)-oriented epitaxial beta-Ga2O3 films grown on (0001) sapphire using halide vapor-phase epitaxy technique with a beta-(Al0.57Ga0.43)(2)O-3 buffer layer. The distinct split of x-ray diffraction rocking curves for (-201) beta-Ga2O3 grown below 950 degrees C was observed, indicative of domain tilt disorders. As quantitatively assessed by transmission electron microscopy, the domain tilt angle significantly decreases from 2.33 degrees to 0.90 degrees along the [132] zone axis and from 2.3 degrees to 0.56 degrees along the [010] zone axis, respectively, as the growth temperature is elevated from 850 to 1100 degrees C. The reduction in tilt disorders is accompanied by the decrease in in-plane domain twist. It indicates that the elimination of small-angle domain boundaries is energetically favorable at high growth temperature above 1000 degrees C. The quantitative investigation on the evolution of domain disorders in beta-Ga2O3 shed light on the pathway to improve epitaxial quality for cutting-edge power electronic and optoelectronic device applications.