Candidate For Field-effect Transistors Research Articles

Design of a 30 nm Germanium FinFET by Parameter Optimization

Germanium (Ge) is envisioned as a suitable channel candidate for field-effect transistors (FET). Properties of Ge such as high carrier mobility, compatibility with Si and adaptability with high-k materials makes it comparable to silicon. This paper presents a detailed design of a 30 nm Ge based FinFET by parameter optimization using Silvaco software. Poisson and Schrodinger equation is used to come up with an analytical quantum model. The quantum model is developed based on theory of a double gate (DG) FET but the final design is a trigate (TG) device since they are more scalable. The quantum attributes of DG MOSFET are acquired by adopting the coupled Poisson–Schrodinger equation with the aid of the variational approach. The ratio of channel length (LC) to fin height (Hfin) to fin thickness (tfin) is 4:2:1. The channel length is taken as the gate length (LG) although they are slightly differ mathematically due to side diffusion of the implanted ions. Simulation results show that physical parameters such as dimensions influence electrical characteristics of the device such as threshold voltage (VTH). Much focus is on optimization of the on/off current ratio (ION/OFF) and VTH performances. ION/OFF≈ 106 is achieved at carrier concentration in the range 1 × 1018≤ nd≤ 1.22 × 1018 and in this scenario, VTH = 0.4V . Systematical investigation is presented using IV characteristics to demonstrate the sensitivity or how critical design parameters of Ge FinFET are to the device’s figure of merits. Device performs well at low voltages but breaks down at higher drain voltages (VDS≥ 4V). Gate source voltages (VGS) range between 0.05V≤ VGS ≤ 1V and conductance is dependent on it. Effects of DIBL, which is around 0.031, and velocity saturation are studied to determine how they can be suppressed during the design process.

Prospects of Terahertz Transistors with the Topological Semimetal Cadmium Arsenide

AbstractElectronic devices that operate at terahertz frequencies will require new materials that exhibit higher carrier velocities than traditional semiconductors. Calculations show that cadmium arsenide, a 3D topological (Dirac) semimetal, is an excellent candidate for field effect transistors that operate at frequencies above 1 THz. Moreover, such transistors have unique advantages that are enabled by the properties of Dirac electrons. These include predictions of an unprecedented linearity of the transconductance and cutoff frequencies over a large operating range and cutoff frequencies that remain above 1 THz at carrier densities as low as 1011 cm−2. The calculations are underpinned by measurements of devices with cadmium arsenide channels. Extremely low contact resistances (<2 × 10−9 Ω cm2), high electron velocities (>7 × 105 m s−1), and unprecedentedly large current densities (up to 10 A mm−1) are demonstrated. Current modulation (>50%) and transconductance already achieved in the early transistors show the potential for large (>10 ×) improvements by reducing interface trap densities. The results demonstrate the significant potential of topological semimetals for high‐speed transistors operating in the THz regime and open up new opportunities for next‐generation RF circuits.

Bulk and few-layer MnPS3: a new candidate for field effect transistors and UV photodetectors

Two dimensional few-layer and bulk MnPS3-based field effect transistors and photodetectors.

BilayerSnS2: Tunable stacking sequence by charging and loading pressure

Employing density functional theory-based methods, we investigate monolayer and bilayer structures of hexagonal SnS$_{2}$, which is recently synthesized monolayer metal dichalcogenide. Comparison of 1H and 1T phases of monolayer SnS$_{2}$ confirms the ground state to be the 1T phase. In its bilayer structure we examine different stacking configurations of the two layers. It is found that the interlayer coupling in bilayer SnS$_{2}$ is weaker than that of typical transition-metal dichalcogenides (TMDs) so that alternative stacking orders have similar structural parameters and they are separated with low energy barriers. Possible signature of the stacking order in SnS$_{2}$ bilayer has been sought in the calculated absorbance and reflectivity spectra. We also study the effects of the external electric field, charging, and loading pressure on the characteristic properties of bilayer SnS$_{2}$. It is found that (i) the electric field increases the coupling between the layers at its prefered stacking order, so the barrier height increases, (ii) the bang gap value can be tuned by the external E-field and under sufficient E-field, the bilayer SnS$_{2}$ can become semi-metal, (iii) the most favorable stacking order can be switched by charging and (iv) a loading pressure exceeding 3 GPa changes the stacking order. E-field tunable bandgap and easy-tunable stacking sequence of SnS$_{2}$ layers make this 2D crystal structure a good candidate for field effect transistor and nanoscale lubricant applications.

Liquid crystals for organic thin-film transistors

Crystalline thin films of organic semiconductors are a good candidate for field effect transistor (FET) materials in printed electronics. However, there are currently two main problems, which are associated with inhomogeneity and poor thermal durability of these films. Here we report that liquid crystalline materials exhibiting a highly ordered liquid crystal phase of smectic E (SmE) can solve both these problems. We design a SmE liquid crystalline material, 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10), for FETs and synthesize it. This material provides uniform and molecularly flat polycrystalline thin films reproducibly when SmE precursor thin films are crystallized, and also exhibits high durability of films up to 200 °C. In addition, the mobility of FETs is dramatically enhanced by about one order of magnitude (over 10 cm2 V−1 s−1) after thermal annealing at 120 °C in bottom-gate-bottom-contact FETs. We anticipate the use of SmE liquid crystals in solution-processed FETs may help overcome upcoming difficulties with novel technologies for printed electronics.

First-principles design of silicene/Sc2CF2 heterojunction as a promising candidate for field effect transistor

Experimentally, it is challenging to epitaxially grow silicene on conventional semiconductor substrate. Here, we explore high-quality van de Waals silicene/Sc2CF2 heterojunction (HTJ) using first-principles calculations, and we predict that the Dirac cone of silicene maintains in the band gap of Sc2CF2 substrate. The nearly linear band dispersion of silicene with a sizable gap (36–48 meV) is obtained in all HTJs due to the sublattice symmetry broken by the intrinsic interface dipole. Remarkably, the band gap of all these HTJs can be effectively modulated by the interlayer spacing and strain. These findings are promising for high-performance FETs with high carrier mobilities operating at room temperature in nanoelectronics.

Transport engineering design of AND and NOR gates with a 1,4-2-phenyl-dithiolate molecule

We have explored logical AND and NOR gate responses of a 1,4-2-phenyl-dithiolate molecule threaded by a magnetic flux ϕ in two-terminal junctions by using the Green's function method in the framework of a nearest-neighbor tight-binding approximation. Here, we put emphasis on the logical gate voltages, and obtain the electrical transmission and current-voltage characteristics with metal-molecule-metal (m-M-m) tunnel junctions. The hopping integral among two neighboring atoms in the molecule was quantitatively estimated by means of density functional theory (DFT) calculations. Our results show that the AND and NOR responses are explored through our molecular junction for a typical value of the magnetic flux. The numerical results may shed light on the next applications of molecular systems and make them a good, promising candidate for field-effect transistors.