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

An amorphous Yb
₂
O
₃
passivation layer integrated with a crystalline ZrTiO
₄
film was explored as the advanced gate stack for Ge MOS devices. The ZrTiO
₄
/Yb
₂
O
₃
gate stack demonstrates Dit of 2.4 × 10
¹¹
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 ZrTiO
₄
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.