1-nm-thick EOT high mobility Ge n- and p-MOSFETs with ultrathin GeOx/Ge MOS interfaces fabricated by plasma post oxidation

An ultrathin EOT Al₂O₃/GeO_x/Ge gate stack with a superior GeO_x/Ge MOS interface has been fabricated with a plasma post oxidation method. The properties of the ultra thin GeO_x/Ge MOS interfaces are examined systemically, and it is revealed that there is a universal relationship between the D_it at GeO_x/Ge interface and the GeO_x thickness, and a 0.5-nm-thick GeO_x (0.35 nm EOT) is sufficient to suppress the D_it. The Ge n- and p-MOSFETs using the Al₂O₃/GeO_x/Ge gate stacks are fabricated on (100), (110) and (111) Ge. High mobility Ge n-MOSFETs with sub-nm EOT have been realized for the first time with record high mobilities of 937 and 691 cm²/Vs at EOT of 1.14 and 0.98 nm. It is found that the sufficient suppression of D_it allows us to obtain high peak mobilities even in sub-nm EOT range, while further improvements in surface roughness and suppression of the density of remaining Coulomb scattering centers such as fixed charges and slow traps are still needed to further enhance the performances of Ge n- and p-MOSFETs.