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

      Researchers from the Leibniz-Institut für Kristallzüchtung (IKZ) have published a dissertation titled "Influencing the morphological stability of MOVPE-grown β-Ga₂O₃ films by O₂/Ga ratio" in Applied Surface Science.

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.

Fig. 1. AFM image of the (1 0 0) β-Ga₂O₃ substrate surface before the film growth. A straight-fronted stepped terrace is visible, ascending from left to right and aligned from top to bottom.

Fig. 2. AFM images showing morphology evolution of (1 0 0) β-Ga₂O₃ films grown by MOVPE under an O₂/Ga ratio of 1250 at different thicknesses: (a) 300 nm, (b) 350 nm, (c) 400 nm, and (d) 500 nm.

DOI：

https://doi.org/10.1016/j.apsusc.2024.159966