Quasi-zero lattice mismatch and band alignment of BaTiO₃ on epitaxial (110)Ge

Growth, structural, and band alignment properties of pulsed laser deposited amorphous BaTiO₃ on epitaxial molecular beam epitaxy grown (110)Ge layer, as well as their utilization in low power transistor are reported. High-resolution x-ray diffraction demonstrated quasi-zero lattice mismatch of BaTiO₃ on (110)Ge. Cross-sectional transmission electron microscopy micrograph confirms the amorphous nature of BaTiO₃ layer as well as shows a sharp heterointerface between BaTiO₃ and Ge with no traceable interfacial layer. The valence band offset, ΔE_v, of 1.99 ± 0.05 eV at the BaTiO₃/(110)Ge heterointerface is measured using x-ray photoelectron spectroscopy. The conduction band offset, ΔE_c, of 1.14 ± 0.1 eV is calculated using the bandgap energies of BaTiO₃ of 3.8 eV and Ge of 0.67 eV. These band offset parameters for carrier confinement and the interface chemical properties of the BaTiO₃/(110)Ge system are significant advancement towards designing Ge-based p-and n-channel metal-oxide semiconductor field-effect transistors for low-power application.