【International Papers】Impact of temperature and film thickness on α- and β- phase formation in Ga₂O₃ thin films grown on a-plane sapphire substrate

      Researchers from the University of Latvia have published a dissertation titled "Impact of temperature and film thickness on α- and β- phase formation in Ga₂O₃ thin films grown on a-plane sapphire substrate " in Thin Solid Films.

Abstract

      The metastable corundum gallium oxide (α-Ga₂O₃) features advantageous properties in comparison to the thermodynamically stable monoclinic β-Ga₂O₃ phase, such as wider bandgap, which is beneficial for a range of applications. However, stabilization of phase-pure α-Ga₂O₃ thin films is still challenging with conventional deposition methods due to limited understanding of growth factor influence on film formation. In this work we investigated the impact of growth temperature (500-800 °C) and film thickness on α- and β-Ga₂O₃ phase formation in thin films deposited heteroepitaxially on a-plane sapphire via reactive pulsed direct-current magnetron sputtering. The structure and morphology of the prepared films was studied using X-ray diffraction, scanning and transmission electron microscopy, selected-area electron diffraction and atomic force microscopy. It was determined that the growth of α-Ga₂O₃ phase is more favourable when the substrate temperature is increased, while polycrystalline β-Ga₂O₃ forms at lower deposition temperatures. Phase-pure α-Ga₂O₃ epitaxial films can be obtained up to some critical thickness, when the β-Ga₂O₃ phase formation starts due to exposed α-phase crystal facets of other than [110] orientation. A-plane sapphire substrates show merit for epitaxial stabilization of thicker single-phase α-Ga₂O₃ thin films, if the complex parameter space of the selected deposition method is considered.

DOI：doi.org/10.1016/j.tsf.2024.140467