Abstract
MoS2 based transistors are being explored as a promising candidate for different applications. The techniques employed to characterize these devices have been directly adapted from 3D semiconductors, without considering the validity of the assumptions. In this work, we discuss the limitations of two-probe (2P), four probe (4P) and transfer length methods (TLM) for extracting electrical parameters. Based on finite-element modeling, we provide design considerations for 4P structures to measure more accurately. Extracting the parameters from these techniques in the appropriate regimes, we identify contact resistance RC to be critical for scaled MoS2 devices. Using 4P and TLM measurements along with temperature dependent measurements, we derive further insights into the behavior of the RC in the subthreshold and linear regime. Additionally, we propose an empirical model for the on-state contact resistance.
Highlights
Technique Discussion and Parameter ExtractionFor the measurements and property extraction MoS2 back-gated 4P-FETs and Transmission Line Measurements (TLM) structures were built
The ever-growing demand in semiconductor industry for faster, denser, efficient and robust technology has been driving the need for innovative solutions
We have compared the validity of different electrical test structures in evaluating parameters such as field mobility, threshold voltage, contact resistance and contact resistivity
Summary
For the measurements and property extraction MoS2 back-gated 4P-FETs and TLM structures were built. By linear extrapolation the contact resistances at the source (RCS) and drain (RC D) are determined independently from the measured potentials in P1 and P2 respectively as shown in Equations 16 and 17. As Equation 22 demonstrates, even a constant transfer length would exhibit a gate-modulated Rc as charge is injected in MoS2 film changing RSH This dependence on RSH gives rise to the 1/VGS modulation for the contact resistance. For VGS > VT H , the barrier width is thin enough (indicated by 0 eV) and tunneling mechanisms could dominate at the contacts leading to the total resistance limited by the heavily doped channel, suggested by the negative temperature coefficient We noticed that the extracted barrier heights differ significantly from the a)
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