Insight on the Characterization of MoS₂Based Devices and Requirements for Logic Device Integration

Abstract

MoS 2 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 R C to be critical for scaled MoS 2 devices. Using 4P and TLM measurements along with temperature dependent measurements, we derive further insights into the behavior of the R C in the subthreshold and linear regime. Additionally, we propose an empirical model for the on-state contact resistance. The ever-growing demand in semiconductor industry for faster, denser, efficient and robust technology has been driving the need for innovative solutions. Though, scaling was very effective in this regard, in recent years there are growing challenges for the conventional three-dimensional (3D) semiconductors.1 One limitation is the reduced electrostatic control of the gate over the device channel as the channel length (L CH ) get smaller. To overcome this problem multigate technologies evolved and FINFET structures has become the de facto standard for high performance devices. However, even these devices face problems due to, among other things, the 3D nature of these devices.2 Another possible solution is to use 2D planar technologies with ultra-thin body semiconductors to allow for better electrostatic control without losing the two-dimensional (2D) nature of the processing and the device. Nevertheless, this cannot be achieved with conventional 3D semiconductors due to performance degradation on thinning below 100 nm. Breaking the out of plane covalent bonds increases the dangling bonds on the surface, resulting in mobility degradation due to surface scattering of electrons. 3In this context, the family of 2D crystals such as graphene and transition metal dichalcogenides (MX 2 ) offer an interesting case to investigate as alternate ultra-thin body channels. The layers being weakly bonded to each other only by Van der Waals forces and no out-of-plane covalent bonds, there are less dangling bonds than in case of thinning down 3D semiconductors. This enables better electrostatic control while avoiding degradation of transport properties. Among the 2D material crystals, MX 2 are specially interesting due to their semi-conductive properties.4-6 They have also been predicted to have robust performance for channel lengths down to 15 nm.7 Molybdenum disulfide (MoS 2 ), is commonly used as a representative of the MX 2 family. It has been demonstrated to be an interesting candidate for different applications such as low power logic devices, spintronic, valleytronic and also photo-voltaic devices. [8][9][10][11][12] It ...

Charge carrier injection and transport engineering in two-dimensional transition metal dichalcogenides

“…Nevertheless, the R C values reported so far range from hundreds to millions of Ω μm depending on the contact approach and the degree of accuracy of the selected method to estimate R C as we next discuss. 42 (i) Two-probe measurement assumes solely thermionic emission with a given SBH ≤ 0.1 eV to evaluate R C = ( h 3 /4π e 2 m * tk B T )exp( qφ B / k B T ), where h , k B , m *, and t are Planck's constant, Boltzmann constant, effective mass, and thickness, respectively. 43 (ii) Two-probe FET measurements extract R C by polynomial fitting b 1 + b 2/ x + b 3/ x 2 of the total resistance ( R T ) vs. V gs as 2 R C = b 1.…”

“… 50 (v) Four-probe FET measurement avoids the potential drop in the sensing probes, and thus R C can be extracted independently for each lead. 42 (vi) The Y-function method is more realistic since it allows the extraction of R C from the FET linear region while considering phonon and surface scattering events as well as the voltage drop induced by the SB. 51 …”

“… 18 , 28 , 32 , 89 , 92 Nonetheless, in a double-gated geometry C g should include both top and bottom gate capacitances. 25 , 31 , 42 , 65 , 66 , 73 Furthermore, as the channel length is scaled down to the electron mean free path, electronic devices are pushed from the diffusion limit to the scattering-free ballistic limit, at which the quantum conductance can potentially reach 2 e 2 / h and the quantum contact resistance can reach 30 Ω μm at a n 2D of 10 13 cm –2 . 22 , 93 …”

Electronic Transport of MoS2 Monolayered Flakes Investigated by Scanning Electrochemical Microscopy

“…This is in accordance with literature regarding the conductive state of MoS 2 transistors. [21,22] Then, as pecific numerical investigation was performed regarding the contact resistance between T 6 and its neighbors. We considered two highly conductingt riangles connected at one of the vertex (see the Supporting Information).…”

“…This is in accordance with literature regarding the conductive state of MoS 2 transistors. [21,22] Then, as pecific numerical investigation was performed regarding the contact resistance between T 6 and its Figure 1, with different dmFc concentrations:0.3 mm (b), 16 mm (c). For both curves, the blue and red colors correspond, respectively to 60 %a nd 150 %o ft he probe current measuredi ns olution( I inf ).…”