High-mobility and low-parasitic resistance characteristics in strained Ge nanowire pMOSFETs with metal source/drain structure formed by doping-free processes

Metal source/drain (S/D) Ge nanowire MOSFETs with a compressive strain as high as 3.8% were fabricated by the 2-step Ge-condensation technique without intentional doping for the S/D. Record high inversion hole mobility (μ_eff = 855 cm²/Vs @ N_s = 5×10¹²cm^-2) and saturation drain current 731μA/μm at V_d=-1V were achieved among Ge nanowire pFETs ever reported. It is found that the extremely low contact resistivity ρ_c ~ 4×10^-8O cm² for the Schottky contact contributes to the high saturation current as well as the high mobility.