Influencing the morphological stability of MOVPE-grown β-Ga2O3 films by O2/Ga ratio

Abstract

The morphology evolution of (100) β-Ga2O3 films grown by metalorganic vapor phase epitaxy (MOVPE) is studied by atomic force microscopy (AFM). In particular, when grown under a high O2/Ga ratio (O2/Ga = 1250) and above a thickness of 350 nm, these films exhibit striking morphological instabilities, including step meandering and bunching, which contribute significantly to surface roughening. Transmission electronic microscopy (TEM) measurements reveal a morphological transition on the growing surface with a coexistence of step-flow and step-bunching growth modes resulting from these instabilities. In contrast, growth conditions with low O2/Ga ratios (O2/Ga = 350) effectively suppress meandering and bunching instabilities, resulting in films with excellent electrical properties. These observations are rationalized through the Burton-Cabrera-Frank (BCF) theory and Bales-Zangwill (BZ) instability (Gibbs-Thompson effect and Mullins-Sekerka instability) , thus bridging theoretical models and the experimental results.