Crystalline ZrTiO$_{\bf 4}$-Gated Ge Metal–Oxide–Semiconductor Devices With Amorphous Yb$_{\bf 2}$ O$_{\bf 3}$

An amorphous Yb₂O₃ passivation layer integrated with a crystalline ZrTiO₄ film was explored as the advanced gate stack for Ge MOS devices. The ZrTiO₄/Yb₂O₃ gate stack demonstrates Dit of 2.4 × 10¹¹ cm^-2· eV^-1 and EOT down to 0.76 nm which are, respectively, due to the formation of an interfacial YbGeO_x layer that well passivates the dangling bonds at Ge surface and the adoption of a crystalline ZrTiO₄ film with a κ value of 45.6. The gate stack also shows low leakage current, tight distribution of device parameters, and desirable reliability performance, paving an alternative avenue to develop high-performance Ge MOS devices.