Influencing the morphological stability of MOVPE-grown β-Ga2O3 films by O2/Ga ratio
Ta‐Shun Chou, A. Akhtar, Saud Bin Anooz, Jana Rehm, Owen Ernst, Palvan Seyidov, Andreas Fiedler, W. Miller, Zbigniew Galazka, T. Remmele, M. Albrecht, Andreas Popp
Abstract
The morphology evolution of (1 0 0) 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.