【Epitaxy Papers】Growth of a-plane BaTiO₃ on a-plane β-Ga₂O₃ by molecular-beam epitaxy

      Researchers from the Cornell University have published a dissertation titled "Growth of a-plane BaTiO₃ on a-plane β-Ga₂O₃ by molecular-beam epitaxy" in APL Materials.

Abstract

      We demonstrate the epitaxial growth of single-phase (100) BaTiO₃ films on (100) β-Ga₂O₃ substrates at substrate temperatures ranging from 600 to 700 °C using molecular-beam epitaxy. Characterization of a 47 nm thick BaTiO₃ film by atomic force microscopy reveals a step-and-terrace morphology with unit-cell-high BaTiO₃ steps and an rms surface roughness of 0.26 nm. Scanning transmission electron microscopy (STEM) images show that in some regions the β-Ga₂O₃ substrate terminates with a (100)A plane as it transitions to BaTiO₃ and in other regions with a (100)B plane. The (100) BaTiO₃ films are fully relaxed and consist of a mixture of two types of a-axis domains: a₁ and a₂. The orientation relationship determined by X-ray diffraction and confirmed by STEM is (100) BaTiO₃ || (100) β-Ga₂O₃ and [011] BaTiO₃||[010] β-Ga₂O₃. Despite the average linear lattice mismatch of 3.8%, BaTiO₃ films with rocking curve full width at half maximum widths as narrow as 28 arc sec are achieved. From capacitance–voltage measurements on a metal–oxide–semiconductor capacitor structure with a-axis BaTiO₃ as the oxide layer and Si-doped β-Ga₂O₃ as the semiconducting layer, we extract a dielectric constant of K₁₁ = 670 for the BaTiO₃ epitaxially integrated with (100) β-Ga₂O₃. We anticipate that this high-K epitaxial dielectric will be useful for electric-field management in β-Ga₂O₃-based device structures.

DOI：

https://doi.org/10.1063/5.0302145