Abstract
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.
Highlights
Junctionless field effect transistors (JLFETs) contain the same concentration of a single doping species across the semiconductor region, have been proposed as one of promising alternatives over conventional fin field-effect transistors (FinFET), which are more complicated to process and costlier to manufacture [1], [4]
It is expected that the JLFETs can maintain scaling down of complementary metal-oxide-semiconductor (CMOS) technology owing to restrained short channel effects (SCEs) by increased effective channel length [1]–[8]
Germanium (Ge) is a feasible candidate, as it is known for its higher mobility and slightly better performance compared to Si when used in JLFETs [10]
Summary
Junctionless field effect transistors (JLFETs) contain the same concentration of a single doping species across the semiconductor region, have been proposed as one of promising alternatives over conventional fin field-effect transistors (FinFET), which are more complicated to process and costlier to manufacture [1], [4]. In turn triggers high Schottky barrier, occurring as a very large hole off-state current [11], [15], [16] For this reason, the MS structure critically disturbs the n-type Ge JLFETs operating in enhancement-mode. The electrical characteristics of JLFETs strongly depend on doping concentration and the dimension of semiconductor nanowires, so the sensitivity of their performance variation by random dopant fluctuation (RDF) is at a highly vulnerable position [6]–[9]. As mentioned above, the effects of severe FLP on JLFET devices are worth considering during performance evaluation as the JLFET with and without MIS S/D structure shows big differences in current characteristics because of Schottky barrier and contact resistivity differences [3]. Without MIS S/D are compared to evaluate the impact of MIS S/D when RDF is applied
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