Epitaxial growth and band alignment of (Gd_xLa_1-x)₂O₃ films on n-GaAs (0 0 1)

Herein we demonstrate the epitaxial stabilization of single-crystalline (Gd_xLa_1-x)₂O₃ films on n-GaAs (0 0 1) with a controlled lattice match. (Gd_xLa_1-x)₂O₃ films have an in-plane epitaxial relationship with a twofold rotation on GaAs (0 0 1). Spectroscopic characterization by photoemission and absorption confirms that the band gap of (Gd_xLa_1-x)₂O₃ film is approximately ∼5.8 eV. However, the conduction band offset is increased by the unpinned Fermi level of the n-GaAs in the (Gd_xLa_1-x)₂O₃ film (x = 0.97). The correlation of the crystalline property and the interfacial band offset by the electrical properties, as probed by capacitance and leakage current measurements, is also discussed.