Contact resistance extraction methods for short- and long-channel carbon nanotube field-effect transistors

Abstract

Three different methods for the extraction of the contact resistance based on both the well-known transfer length method (TLM) and two variants of the Y-function method have been applied to simulation and experimental data of short-and long-channel CNTFETs. While for TLM special CNT test structures are mandatory, standard electrical device characteristics are sufficient for the Y-function methods. The methods have been applied to CNTFETs with low and high channel resistance. It turned out that the standard Y-function method fails to deliver the correct contact resistance in case of a relatively high channel resistance compared to the contact resistances. A physics-based validation is also given for the application of these methods based on applying traditional Si MOSFET theory to quasi-ballistic CNTFETs.

Accuracy of Y-function methods for parameters extraction of two-dimensional FETs across different technologies

“…with (2 ) considering , is given by (see (3 )), however, is extracted in YFM without using . This approach, previously introduced for silicon‐based devices [20 ], has been adapted and successfully applied to other emerging transistor technologies [14 ] and use for the first time here for 2D FETs.…”

“…the transfer length method (TLM) [5, 13 ]. An evaluation of the YFM extracted values accuracy is to evaluate the closeness of the considered model, including the extracted parameters [5, 12, 14 ] with the experimental data. This verification step has been either rarely provided in 2D FET technologies [6–11 ] or it has been considered for one single transfer curve at low fields of a specific technology [5 ].…”

A Review of Carbon Nanotubes Field Effect-Based Biosensors

“…Thus, the resistance measured is a linear combination (sum) of the contact resistance of the first contact and the second contact, and the sheet resistance of the CNT channel in-between the contacts (i.e. R Tot = 2R C + R Ch ) [83]. It is important to note that the metal resistance is negligibly much smaller than the contact resistance to be considered.…”

“…Shorter channels contribute fewer scattering events, and thus, lower R Ch . In ohmic contacts with ballistic charge transport, the total resistance may approach the quantum limit of the nanotube; R Q = 6.5 k [32], [83]. For the measured total resistances of the variant lengths, the contact resistance is extrapolated by dragging back to L Ch = 0 in the transfer length plot, as illustrated in Fig.…”

“…6 [76], [84]. Results obtained from TLM can be further verified using Y-function method (YFM), which is a numerical parameters extraction method that combines both the drain current and the transconductance transfer characteristics [49], [83]. Table 2 shows the resulting R c and other electrical parameters.…”