Enhanced epitaxial growth of Ga2O3 using an ultrathin SnO2 layer

The tin-enhanced growth of Ga2O3 on (0001) Al2O3 by plasma-assisted molecular beam epitaxy using an ultrathin δ-layer of SnO2 is demonstrated. It is shown that this growth method results in a significantly reduced incorporation of residual Sn in the Ga2O3 film compared to the case of permanent Sn-supply. The ultrathin SnO2 layer, pre-deposited on the substrate, is sufficient to initiate phase pure growth of ε-Ga2O3 in metal-rich growth conditions where otherwise no growth occurs. The chemical and morphological properties of the δ-layer are analyzed and the presence of SnO2 on the surface during the entire growth process is demonstrated. Furthermore, we show that this layer is stable during Ga-induced back-etching of a Ga2O3 film. Its impact on the kinetics of Ga2O3 growth is also discussed.