Epitaxial growth and characterization of Gd2O3-doped HfO2 film on Ge (001) substrates with zero interface layer

The GHO (Gd2O3-doped HfO2) films were epitaxially grown on Ge (001) substrates adopting cube-on-cube mode with zero interface layer using pulsed laser deposition (PLD). Reflection high-energy electron diffraction (RHEED) and high-resolution transmission electron microscopy (HRTEM) observation revealed a sharp interface of GHO/Ge and orientation relationship corresponding to (001)GHO//(001)Ge and [011] GHO//[011]Ge. The band offset for GHO/Ge stack was evaluated to be 3.92 eV for valence band and 1.38 eV for conduction band by X-ray photoelectron spectrum. Small equivalent oxide thickness (0.49 nm) and interface state density (7×1011 cm−2) were achieved from Au/Ti/GHO/Ge/Al capacitors.

Graphical abstract(a) Cross-sectional HRTEM micrograph of GHO thin film grown directly on Ge (001) surface at 660 °C; (b) Enlarged drawing of rectangular region in (a); (e*), (f*), and (c) are the corresponding FFT patterns for the Ge substrate (e), GHO layer (f), and GHO/Ge regions in (b), respectivelyFigure optionsDownload full-size imageDownload as PowerPoint slide