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Anisur Rahman

Bio: Anisur Rahman is an academic researcher from Purdue University. The author has contributed to research in topics: Effective mass (solid-state physics) & Quantum simulator. The author has an hindex of 11, co-authored 15 publications receiving 1719 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, numerical simulations are used to guide the development of a simple analytical theory for ballistic field-effect transistors, and the model reduces to Natori's theory of the ballistic MOSFET.
Abstract: Numerical simulations are used to guide the development of a simple analytical theory for ballistic field-effect transistors. When two-dimensional (2-D) electrostatic effects are small (and when the insulator capacitance is much less than the semiconductor (quantum) capacitance), the model reduces to Natori's theory of the ballistic MOSFET. The model also treats 2-D electrostatics and the quantum capacitance limit where the semiconductor quantum capacitance is much less than the insulator capacitance. This new model provides insights into the performance of MOSFETs near the scaling limit and a unified framework for assessing and comparing a variety of novel transistors.

740 citations

Journal ArticleDOI
TL;DR: An analytically compact model for the double-gate metal-oxide semiconductor field effect transistor (MOSFET) based on McKelvey's flux theory is developed in this article.
Abstract: An analytically compact model for the nanoscale double gate metal-oxide semiconductor field effect transistor (MOSFET) based on McKelvey's flux theory is developed. The model is continuous above and below threshold and from the linear to saturation regions. Most importantly, it describes nanoscale MOSFETs from the diffusive to ballistic regimes. In addition to its use in exploring the limits and circuit applications of double gate MOSFETs, the model also serves as an example of how semiclassical scattering theory can be used to develop physically sound models for nanoscale transistors.

184 citations

Journal ArticleDOI
Jing Wang1, Anisur Rahman1, Avik W. Ghosh1, Gerhard Klimeck1, Mark Lundstrom1 
TL;DR: In this article, the parabolic effective-mass model with bulk effective-masses significantly overestimates SNWT threshold voltages when the wire width is < 3 nm, and ON-currents when the wires width is less than 5 nm.
Abstract: This paper examines the validity of the widely used parabolic effective-mass approximation for computing the current-voltage (I-V) characteristics of silicon nanowire transistors (SNWTs). The energy dispersion relations for unrelaxed Si nanowires are first computed by using an sp/sup 3/d/sup 5/s/sup */ tight-binding (TB) model. A seminumerical ballistic field-effect transistor model is then adopted to evaluate the I-V characteristics of the (n-type) SNWTs based on both a TB dispersion relation and parabolic energy bands. In comparison with the TB approach, the parabolic effective-mass model with bulk effective-masses significantly overestimates SNWT threshold voltages when the wire width is <3 nm, and ON-currents when the wire width is <5 nm. By introducing two analytical equations with two tuning parameters, however, the effective-mass approximation can well reproduce the TB I-V results even at a /spl sim/1.36-nm wire width.

184 citations

Journal ArticleDOI
TL;DR: In this article, a general theory for quantum simulation of cubic semiconductor n-type metal-oxide-semiconductor field effect transistors is presented within the effective mass equation approach.
Abstract: The general theory for quantum simulation of cubic semiconductor n-type metal-oxide-semiconductor field-effect transistors is presented within the effective-mass equation approach. The full three-dimensional transport problem is described in terms of coupled transverse subband modes which arise due to quantum confinement along the body thickness direction. Couplings among the subbands are generated for two reasons: due to spatial variations of the confinement potential along the transport direction and due to nonalignment of the device coordinate system with the principal axes of the constant energy conduction-band ellipsoids. The problem simplifies considerably if the electrostatic potential is separable along the transport and confinement directions, and further if the potential variations along the transport direction are slow enough to prevent dipolar coupling (Zener tunneling) between subbands. In this limit, the transport problem can be solved by employing two unitary operators to transform an arbit...

160 citations

Journal ArticleDOI
TL;DR: In this paper, the parabolic effective-mass model with bulk effective-masses significantly overestimates SNWT threshold voltages when the wire width is < 3nm, and ON-currents when the wires width is ≥ 5nm.
Abstract: This paper examines the validity of the widely-used parabolic effective-mass approximation for computing the current-voltage (I-V) characteristics of silicon nanowire transistors (SNWTs). The energy dispersion relations for unrelaxed Si nanowires are first computed by using an sp3d5s* tight-binding model. A semi-numerical ballistic FET model is then adopted to evaluate the I-V characteristics of the (n-type) SNWTs based on both a tight-binding dispersion relation and parabolic energy bands. In comparison with the tight-binding approach, the parabolic effective-mass model with bulk effective-masses significantly overestimates SNWT threshold voltages when the wire width is <3nm, and ON-currents when the wire width is <5nm. By introducing two analytical equations with two tuning parameters, however, the effective-mass approximation can well reproduce the tight-binding I-V results even at a \~1.36nm wire with.

141 citations


Cited by
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Journal ArticleDOI
Ali Javey1, Jing Guo2, Qian Wang1, Mark Lundstrom2, Hongjie Dai1 
07 Aug 2003-Nature
TL;DR: It is shown that contacting semiconducting single-walled nanotubes by palladium, a noble metal with high work function and good wetting interactions with nanotube, greatly reduces or eliminates the barriers for transport through the valence band of nanot tubes.
Abstract: A common feature of the single-walled carbon-nanotube field-effect transistors fabricated to date has been the presence of a Schottky barrier at the nanotube–metal junctions1,2,3. These energy barriers severely limit transistor conductance in the ‘ON’ state, and reduce the current delivery capability—a key determinant of device performance. Here we show that contacting semiconducting single-walled nanotubes by palladium, a noble metal with high work function and good wetting interactions with nanotubes, greatly reduces or eliminates the barriers for transport through the valence band of nanotubes. In situ modification of the electrode work function by hydrogen is carried out to shed light on the nature of the contacts. With Pd contacts, the ‘ON’ states of semiconducting nanotubes can behave like ohmically contacted ballistic metallic tubes, exhibiting room-temperature conductance near the ballistic transport limit of 4e2/h (refs 4–6), high current-carrying capability (∼25 µA per tube), and Fabry–Perot interferences5 at low temperatures. Under high voltage operation, the current saturation appears to be set by backscattering of the charge carriers by optical phonons. High-performance ballistic nanotube field-effect transistors with zero or slightly negative Schottky barriers are thus realized.

3,126 citations

Book
Yuan Taur1, Tak H. Ning1
01 Jan 2016
TL;DR: In this article, the authors highlight the intricate interdependencies and subtle tradeoffs between various practically important device parameters, and also provide an in-depth discussion of device scaling and scaling limits of CMOS and bipolar devices.
Abstract: Learn the basic properties and designs of modern VLSI devices, as well as the factors affecting performance, with this thoroughly updated second edition. The first edition has been widely adopted as a standard textbook in microelectronics in many major US universities and worldwide. The internationally-renowned authors highlight the intricate interdependencies and subtle tradeoffs between various practically important device parameters, and also provide an in-depth discussion of device scaling and scaling limits of CMOS and bipolar devices. Equations and parameters provided are checked continuously against the reality of silicon data, making the book equally useful in practical transistor design and in the classroom. Every chapter has been updated to include the latest developments, such as MOSFET scale length theory, high-field transport model, and SiGe-base bipolar devices.

2,680 citations

Book
17 Oct 2007
TL;DR: FinFETs and Other Multi-Gate Transistors provides a comprehensive description of the physics, technology and circuit applications of multigate field-effect transistors (FET) and explains the physics and properties.
Abstract: FinFETs and Other Multi-Gate Transistors provides a comprehensive description of the physics, technology and circuit applications of multigate field-effect transistors (FETs). It explains the physics and properties of these devices, how they are fabricated and how circuit designers can use them to improve the performances of integrated circuits. The International Technology Roadmap for Semiconductors (ITRS) recognizes the importance of these devices and places them in the "Advanced non-classical CMOS devices" category. Of all the existing multigate devices, the FinFET is the most widely known. FinFETs and Other Multi-Gate Transistors is dedicated to the different facets of multigate FET technology and is written by leading experts in the field.

843 citations

Journal ArticleDOI
TL;DR: In this paper, the physics of charge control, source velocity saturation due to thermal injection, and scattering in ultrasmall MOSFETs are examined. And the results show that the essential physics of nanoscale MOSFLETs can be understood in terms of a conceptually simple scattering model.
Abstract: The device physics of nanoscale MOSFETs is explored by numerical simulations of a model transistor. The physics of charge control, source velocity saturation due to thermal injection, and scattering in ultrasmall devices are examined. The results show that the essential physics of nanoscale MOSFETs can be understood in terms of a conceptually simple scattering model.

536 citations

Journal ArticleDOI
TL;DR: In this article, the performance limits of monolayer transition metal dichalcogenide ( MX2) transistors with a ballistic MOSFET model were examined with an ab initio theory.
Abstract: The performance limits of monolayer transition metal dichalcogenide ( MX2) transistors are examined with a ballistic MOSFET model. Using an ab initio theory, we calculate the band structures of 2-D transition MX2. We find the lattice structures of monolayer MX2 remain the same as the bulk MX2. Within the ballistic regime, the performances of monolayer MX2 transistors are better compared with those of the silicon transistors if a thin high-κ gate insulator is used. This makes monolayer MX2 promising 2-D materials for future nanoelectronic device applications.

463 citations