Ge CMOS: Breakthroughs of nFETs (Imax=714 mA/mm, gmax=590 mS/mm) by recessed channel and S/D

We report a new approach to realize the Ge CMOS technology based on the recessed channel and source/drain (S/D). Both junctionless (JL) nFETs and pFETs are integrated on a common GeOI substrate. The recessed S/D process greatly improves the Ge n-contacts. A record high maximum drain current (I_max) of 714 mA/mm and trans-conductance (g_max) of 590 mS/mm, high I_on/I_off ratio of 1×10⁵ are archived at channel length (L_ch) of 60 nm on the nFETs. Scalability studies on Ge nFETs are conducted in sub-100 nm region down to 25 nm for the first time. Considering the Fermi level (E_F) pining near the valence band edge (EV) of Ge, a novel hybrid CMOS structure with the inversion-mode (IM) Ge pFET and the JL accumulation-mode (JAM) Ge nFET is proposed.