From Fowler–Nordheim to Nonequilibrium Green’s Function Modeling of Tunneling

IEEE Electron Device Lett.

Klimeck

Rahman

2016

Self Cite

Abstract-The main promise of tunnel FETs (TFETs) is to enable supply voltage (VDD) scaling in conjunction with dimension scaling of transistors to reduce power consumption. However, reducing VDD and channel length (L ch ) typically deteriorates the ON-and OFF-state performance of TFETs, respectively. Accordingly, there is not yet any report of a high performance TFET with both low VDD (∼0.2V) and small L ch (∼6nm). In this work, it is shown that scaling TFETs in general requires scaling down the bandgap Eg and scaling up the effective mass m * for high performance. Quantitatively, a channel material with an optimized bandgap (Eg ∼ 1.2qVDD [eV ]) and an engineered effective mass (m * −1 ∼ 40V 2.50 ]) makes both VDD and L ch scaling feasible with the scaling rule of L ch /VDD = 30 nm/V for L ch from 15nm to 6nm and corresponding VDD from 0.5V to 0.2V.

Section: Simulation Resultsmentioning

confidence: 99%

“…I ON /I OFF ≈ 10 10 4 ). Roughly, the transmission in the ON-state (T ON ) and OFFstate (T OFF ) of TFETs depends on [15], [16]:…”

Section: Introductionmentioning

confidence: 99%

Can Homojunction Tunnel FETs Scale Below 10 nm?

IEEE Electron Device Lett.

Klimeck

Rahman

2016

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“…This compact equation quantitatively represents the trend of sophisticated atomistic simulations, although it assumes a simple potential distribution and a simple m * [11], Different materials that have the same Λ m * E g are expected to provide I ON within the same order of magnitude. However, we find minor deviations between different materials because this compact equation approximates complex band structures by a single band reduced effective mass and ignores contributions from higher sub-bands.…”

Section: Appendix I How Descriptive Is Imentioning

confidence: 99%

“…I ON is proportional to the BTBT transmission probability (T BT BT ) which can be expressed in terms of both electrostatics and material properties [11] as…”

Section: Introductionmentioning

confidence: 99%

Channel Thickness Optimization for Ultrathin and 2-D Chemically Doped TFETs

Chen

Ameen

IEEE Trans. Electron Devices

et al. 2018

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2D material based tunnel FETs are among the most promising candidates for low power electronics applications, since they offer ultimate gate control and high current drives that are achievable through small tunneling distances (Λ) during the device operation. The ideal device is characterized by a minimized Λ. However, devices with the thinnest possible body do not necessarily provide the best performance. For example, reducing the channel thickness (T ch ) increases the depletion width in the source which can be a significant part of the total Λ. Hence, it is important to determine the optimum T ch for each channel material individually. In this work, we study the optimum T ch for three channel materials: WSe2, Black Phosphorus (BP), and InAs using full-band self-consistent quantum transport simulations. To identify the ideal T ch for each material at a specific doping density, a new analytic model is proposed and benchmarked against the numerical simulations.

“…4 shows a constant ONcurrent plot. Notice that I ON depends exponentially on the product of Λ and m * r E g and since both axes are plotted on a logarithmic scale, constant current contours appear as parallel lines [27]. To achieve a higher I ON , one can reduce Λ or m * r E g .…”

Section: A Chemically Doped Tmd Tfetsmentioning

confidence: 99%

Design Rules for High Performance Tunnel Transistors From 2-D Materials

IEEE J. Electron Devices Soc.

Klimeck

Appenzeller

et al. 2016

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Tunneling field-effect transistors (TFETs) based on 2D materials are promising steep sub-threshold swing (SS) devices due to their tight gate control. There are two major methods to create the tunnel junction in these 2D TFETs: electrical and chemical doping. In this work, design guidelines for both electrically and chemically doped 2D TFETs are provided using full band atomistic quantum transport simulations in conjunction with analytic modeling. Moreover, several 2D TFETs' performance boosters such as strain, source doping, and equivalent oxide thickness (EOT) are studied. Later on, these performance boosters are analyzed within a novel figureof-merit plot (i.e. constant ON-current plot). II. INTRODUCTIONTransistor scaling has driven device designs toward thinner channels for better gate control over the channel. 2D materials can provide a shortcut to the ultimate channel thickness scaling: an atomically thin channel. A tight gate control is important in FETs to obtain a 1-to-1 band movement in the channel potential with respect to the gate voltage. The tight gate control is even more crucial for the performance of tunnel FETs (TFETs) [1], [2] since the scaling length and accordingly tunneling distance decreases with a better gate control [3], [4], [6]- [11]. The exponential dependence of the tunneling current on the tunneling distance emphasizes the role of a thin channel and tight gate control in TFETs.Some 2D materials, such as graphene or silicene suffer from the lack of a bandgap (E g ) and are not suitable for transistor applications. On the other hand, 2D materials such as transition metal dichacogenides (TMD: MoS 2 , WSe 2 , MoTe 2 , etc.) exhibit a sizable direct bandgap in their monolayer configuration. Among those, monolayer WTe 2 shows particular promise for high performance TFET applications [4] due to its rather small effective mass and an expected bandgap of about 0.75eV [15]. Note that a bandgap of about (1.1 − 1.5)qV DD provides the best performance in TFETs, where V DD is the supply voltage [12], which means that for a V DD of about 0.5V an E g range of 0.55-0.75eV is expected to provide best performance. Unfortunately, however, experiments indicate that the WTe 2 2H phase may not be stable [16].