Formation of the yttrium/germanium interface: Fermi-level pinning and intermixing at room temperature

Understanding interfacial phenomena is crucial for precise control in the growth of materials for advanced semiconductor devices. A systematic in situ coverage dependent study is conducted to study the Schottky barrier evolution and chemical reactions at the yttrium/germanium interface. Adatom-induced band bending is present in the early growth stages while metal-induced gap states resulted in strong Fermi level pinning at larger yttrium (Y) thicknesses. Furthermore, significant intermixing occurs at 3 A thickness of Y and saturates at 17 A of Y. The underlying mechanism behind this self-limiting intermixing is well-described by a combination of chemical bond and metal-induced weakening theories. The implications of our findings on device performance are discussed.