High-Performance Ge Metal-Oxide-Semiconductor Field-Effect Transistors with a Gate Stack Fabricated by Ultrathin SiO2/GeO2 Bilayer Passivation

We fabricated Ge n- and p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with (100) surface orientation by the gate-last process. The source/drain junctions for n- and p-MOSFETs were fabricated by thermal diffusion of P and ion implantation of B, respectively, which indicated high on/off ratios. An ultrathin SiO2/GeO2 interlayer was used for fabricating the gate stack. The fabricated MOSFETs showed excellent electrical characteristics with a low interface state density. The peak electron and hole mobilities were 1097 and 376 cm(2) V-1 s(-1), respectively, despite the very thin GeO2 thickness (2 nm). These are 1.5-1.6 times higher than those of Si MOSFETs. (C) 2011 The Japan Society of Applied Physics