Role of Gallium Supersaturation in Governing the Heteroepitaxial Growth and Structural Quality of β-Ga2O3 on 4H-SiC

Abstract

A thermodynamic supersaturation framework was developed to characterize the metal–organic chemical vapor deposition of β-Ga2O3 on 4H-SiC. The model describes the fundamental driving force by accounting for the competition between gallium oxide deposition and the desorption of volatile gallium suboxides. To evaluate the systematic influence of gallium supersaturation on film properties, growth was investigated across a four-point experimental matrix spanning over an order of magnitude in supersaturation. Structural analysis employing Williamson–Hall fitting of X-ray diffraction rocking curves revealed that lateral coherence length, mosaic tilt, and dislocation density are directly governed by the magnitude of the driving force, as interpreted through classical nucleation theory. In-depth texture and microstructural characterization using reciprocal space maps (RSMs) and pole figure analysis revealed that the films consist of {2̅ 0 1}, two symmetry-equivalent {3 1 0} and {3 1̅ 0}, and {1 0 1} texture components, all of which exhibit an arrangement analogous to cubic close-packing with an in-plane surface structure of hexagonal symmetry. The volume fraction of the {2̅ 0 1} texture component was found to progressively dominate the film as supersaturation was reduced relative to the {3 1 0}/{3 1̅ 0} components, while the {1 0 1} texture was observed to remain confined near the film–substrate interface. Macroscopic kinetic investigations further established that experimental growth rates follow the behavior predicted by the simulated supersaturation, confirming its role in dictating the net incorporation rate of growth species. Finally, the potential of supersaturation as a transferable growth descriptor was explored by preparing films under disparate combinations of temperature, pressure, and VI/III ratio that yielded nearly identical calculated supersaturation values; these films exhibited comparable crystal quality and highly similar step-terrace surface morphologies. This work suggests that seemingly distinct growth conditions governed by equivalent supersaturation values tend to yield comparable outcomes, highlighting the utility of supersaturation as a physically grounded, transferable descriptor for the consistent optimization of heteroepitaxial growth.