All pulications (111)
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61:Title: Ilatikhameneh H; Ameen TA; Klimeck G; Appenzeller J; Rahman R, 2015, 'Dielectric Engineered Tunnel Field-Effect Transistor', IEEE Electron Device Letters, vol. 36, pp. 1097 - 1100Year : 2015
Publication Type: Journal Papers
Topic:
Abstract
The dielectric engineered tunnel field-effect transistor (DE-TFET) as a high-performance steep transistor is proposed. In this device, a combination of high-k and low-k dielectrics results in a high electric field at the tunnel junction. As a result, a record ON-current of ~1000 μA/μm and a subthreshold swing (SS) below 20 mV/decade are predicted for WTe 2 DE-TFET. The proposed TFET works based on a homojunction channel and electrically doped contacts both of which are immune to interface states, dopant fluctuations, and dopant states in the bandgap, which typically deteriorate the OFF-state performance and SS in the conventional TFETs.
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62:Title: Salazar RB; Ilatikhameneh H; Rahman R; Klimeck G; Appenzeller J, 2015, 'A predictive analytic model for high-performance tunneling field-effect transistors approaching non-equilibrium Green's function simulations', Journal of Applied Physics, vol. 118Year : 2015
Publication Type: Journal Papers
Topic:
Abstract
A new compact modeling approach is presented which describes the full current-voltage (I-V) characteristic of high-performance (aggressively scaled-down) tunneling field-effect-transistors (TFETs) based on homojunction direct-bandgap semiconductors. The model is based on an analytic description of two key features, which capture the main physical phenomena related to TFETs: (1) the potential profile from source to channel and (2) the elliptic curvature of the complex bands in the bandgap region. It is proposed to use 1D Poisson's equations in the source and the channel to describe the potential profile in homojunction TFETs. This allows to quantify the impact of source/drain doping on device performance, an aspect usually ignored in TFET modeling but highly relevant in ultra-scaled devices. The compact model is validated by comparison with state-of-the-art quantum transport simulations using a 3D full band atomistic approach based on non-equilibrium Green's functions. It is shown that the model reproduces with good accuracy the data obtained from the simulations in all regions of operation: the on/off states and the n/p branches of conduction. This approach allows calculation of energy-dependent band-to-band tunneling currents in TFETs, a feature that allows gaining deep insights into the underlying device physics. The simplicity and accuracy of the approach provide a powerful tool to explore in a quantitatively manner how a wide variety of parameters (material-, size-, and/or geometry-dependent) impact the TFET performance under any bias conditions. The proposed model presents thus a practical complement to computationally expensive simulations such as the 3D NEGF approach.
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63:Title: Ilatikhameneh H; Tan Y; Novakovic B; Klimeck G; Rahman R; Appenzeller J, 2015, 'Tunnel Field-Effect Transistors in 2-D Transition Metal Dichalcogenide Materials', IEEE Journal on Exploratory Solid-State Computational Devices and Circuits, vol. 1, pp. 12 - 18Year : 2015
Publication Type: Journal Papers
Topic:
Abstract
In this paper, the performance of tunnel field-effect transistors (TFETs) based on 2-D transition metal dichalcogenide (TMD) materials is investigated by atomistic quantum transport simulations. One of the major challenges of TFETs is their low ON-currents. 2-D material-based TFETs can have tight gate control and high electric fields at the tunnel junction, and can, in principle, generate high ON-currents along with a subthreshold swing (SS) smaller than 60 mV/decade. Our simulations reveal that high-performance TMD TFETs not only require good gate control, but also rely on the choice of the right channel material with optimum bandgap, effective mass, and source/drain doping level. Unlike previous works, a full-band atomistic tight-binding method is used self-consistently with 3-D Poisson equation to simulate ballistic quantum transport in these devices. The effect of the choice of the TMD material on the performance of the device and its transfer characteristics are discussed. Moreover, the criteria for high ON-currents are explained with a simple analytic model, showing the related fundamental factors. Finally, the SS and energy delay of these TFETs are compared with conventional CMOS devices.
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64:Title: Li W; Sharmin S; Ilatikhameneh H; Rahman R; Lu Y; Wang J; Yan X; Seabaugh A; Klimeck G; Jena D; Fay P, 2015, 'Polarization-Engineered III-Nitride Heterojunction Tunnel Field-Effect Transistors', IEEE Journal on Exploratory Solid-State Computational Devices and Circuits, vol. 1, pp. 28 - 34Year : 2015
Publication Type: Journal Papers
Topic:
Abstract
The concept and simulated device characteristics of tunneling field-effect transistors (TFETs) based on III-nitride heterojunctions are presented for the first time. Through polarization engineering, interband tunneling can become significant in III-nitride heterojunctions, leading to the potential for a viable TFET technology. Two prototype device designs, inline and sidewall-gated TFETs, are discussed. Polarization-assisted p-type doping is used in the source region to mitigate the effect of the deep Mg acceptor level in p-type GaN. Simulations indicate that TFETs based on III-nitride heterojunctions can be expected to achieve ON/OFF ratios of 106 or more, with switching slopes well below 60 mV/decade, ON-current densities approaching 100 μA/μm, and energy delay products as low as 67 aJ-ps/μm.
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65:Title: Chu T; Ilatikhameneh H; Klimeck G; Rahman R; Chen Z, 2015, 'Electrically Tunable Bandgaps in Bilayer MoS2', Nano Letters, vol. 15, pp. 8000 - 8007Year : 2015
Publication Type: Journal Papers
Topic:
Abstract
Artificial semiconductors with manufactured band structures have opened up many new applications in the field of optoelectronics. The emerging two-dimensional (2D) semiconductor materials, transition metal dichalcogenides (TMDs), cover a large range of bandgaps and have shown potential in high performance device applications. Interestingly, the ultrathin body and anisotropic material properties of the layered TMDs allow a wide range modification of their band structures by electric field, which is obviously desirable for many nanoelectronic and nanophotonic applications. Here, we demonstrate a continuous bandgap tuning in bilayer MoS2 using a dual-gated field-effect transistor (FET) and photoluminescence (PL) spectroscopy. Density functional theory (DFT) is employed to calculate the field dependent band structures, attributing the widely tunable bandgap to an interlayer direct bandgap transition. This unique electric field controlled spontaneous bandgap modulation approaching the limit of semiconductor-to-metal transition can open up a new field of not yet existing applications.
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66:Title: Ilatikhameneh H; Chen FW; Rahman R; Klimeck G, 2015, 'Electrically doped 2D material tunnel transistor', in 18th International Workshop on Computational Electronics, IWCE 2015Year : 2015
Publication Type: Conference Proceeding
Topic:
Abstract
Gate controlled tunnel junctions wherein the PN-junction like potential profile is made by two gates with opposite polarities are currently dominant in the fabrication of 2D material devices. Electrical doping methods are also preferred in tunnel field-effect transistors (TFETs) as chemical doping introduces states within the bandgap of the semiconductor and therefore degrades the OFF-state performance of TFETs. Moreover, low band gap 2D materials are preferable for high performance TFETs. Consequently, bilayer graphene (BLG) TFET is studied in this work. The critical design parameters in the performance of low bandgap electrically doped 2D transistors are investigated here. Through atomistic simulations, it is shown that the key element in the performance of electrically gated junctions is the thickness of the oxide even when the top and bottom gates have different biases. But still the equivalent oxide thickness (EOT) cannot be disregarded completely since it determines the value of the electric field dependent band gap in BLG.
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67:Title: Tan YHM; Ryu H; Weber B; Lee S; Rahman R; Hollenberg LCL; Simmons MY; Klimeck G, 2015, 'Statistical modeling of ultra-scaled donor-based silicon phosphorus devices', in 2014 Silicon Nanoelectronics Workshop, SNW 2014Year : 2015
Publication Type: Conference Proceeding
Topic:
Abstract
Donor-based silicon phosphorus devices are regarded as promising candidates for quantum computing architectures. The precise number of donors in an ultra-scaled silicon phosphorus double donor-dot device [1] is determined via comparison of theoretically modeled binding energy confidence bands with experimental charge stability diagram measurements. High fidelity of modeling results are enabled through a comprehensive analysis of atomistic dopant placement fluctuations.
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68:Title: Weber B; Tan YHM; Mahapatra S; Watson TF; Ryu H; Lee S; Rahman R; Hollenberg LCL; Klimeck G; Simmons MY, 2015, 'Silicon at the fundamental scaling limit-atomic-scale donor-based quantum electronics', in 2014 Silicon Nanoelectronics Workshop, SNW 2014Year : 2015
Publication Type: Conference Proceeding
Topic:
Abstract
On the route to scalability in donor-based quantum computing architectures, we report on recent advances in the atomic-precision engineering of donor-based electronic devices in silicon, fabricated by STM hydrogen lithography, gas-phase δ-doping, and silicon homoepitaxy [1-3].
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69:Title: Mohiyaddin FA; Rahman R; Kalra R; Lee S; Klimeck G; Hollenberg LCL; Yang CH; Rossi A; Dzurak AS; Morello A, 2015, 'Designing a large scale quantum computer with atomistic simulations', in 2014 Silicon Nanoelectronics Workshop, SNW 2014Year : 2015
Publication Type: Conference Proceeding
Topic:
Abstract
We present atomistic modeling and design of nanostructures, required to demonstrate the essential ingredients-spin readout, control, exchange and transport-of a spin based quantum computer in silicon.
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70:Title: Dielectric Engineered Tunnel FET”, H. Ilatikhameneh, R. Rahman, G. Klimeck, Purdue University, IN, USA, 7/27/2015, US-patent application 62/197513Year : 2015
Publication Type: Patents
Topic: STM Electronics
Abstract
The dielectric engineered tunnel field-effect transistor (DE-TFET) as a high-performance steep transistor is proposed. In this device, a combination of high-k and low-k dielectrics results in a high electric field at the tunnel junction. As a result, a record ON-current of ~1000 μA/μm and a subthreshold swing (SS) below 20 mV/decade are predicted for WTe 2 DE-TFET. The proposed TFET works based on a homojunction channel and electrically doped contacts both of which are immune to interface states, dopant fluctuations, and dopant states in the bandgap, which typically deteriorate the OFF-state performance and SS in the conventional TFETs.
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