Impact of Random Dopant Fluctuation on n-Type Ge Junctionless FinFETs with Metal–Interlayer–Semiconductor Source/Drain Contact Structure

The impact of random dopant fluctuation (RDF) on n-type Ge junctionless FinFETs (JLFETs) with metal–interlayer-semiconductor (MIS) source/drain (S/D) contact structure is firstly investigated via 3-D technology computer aided design (TCAD) simulations. The estimation and evaluation of standard deviations in threshold voltage (Vth), on-state current (Ion), off-state current (Ioff), subthreshold swing (SS), and drain induced barrier lowering (DIBL) by different Ge nanowire doping concentrations and different heights for RDF effects are performed. The results show a decreasing trend of RDF with lower doping concentration of the device. Furthermore, the influence of MIS S/D on RDF of n-type Ge JLFET is assessed through a comparative analysis between an n-type Ge JLFETs with and without MIS S/D structure. The analysis results estimate that MIS S/D can reduce performance variation to approximately 0.0237 V for ${\sigma }~\text{V}_{\mathrm{ th}}$ , 5.75 $\times \,\,10^{-5}$ A/ $\mu {\mathrm{ m}}$ for ${\sigma }~\text{I}_{\mathrm{ on}}$ , 4.30 $\times \,\,10^{-10}$ A/ $\mu {\mathrm{ m}}$ for ${\sigma }~\text{I}_{\mathrm{ off}}$ , 0.548 mV/dec for ${\sigma }$ SS, and 12.3 mV/V for DIBL, without severe performance degradation of the current nominal values. This estimation gives a significant insight on variability prediction of the 7 nm n-type Ge JLFET device with MIS S/D structure.