Conference Proceeding (25)
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11: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
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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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12:Title: Ilatikhameneh H; Klimeck G; Rahman R, 2015, '2D tunnel transistors for ultra-low power applications: Promises and challenges', in 2015 4th Berkeley Symposium on Energy Efficient Electronic Systems, E3S 2015 - ProceedingsYear : 2015
Publication Type: Conference Proceeding
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Abstract
Summary form only given. Tunnel field-effect (TFET) transistors [1] are among the most promising devices for future low-power electronics [2]. However, TFETs usually suffer from low ON-current values. Recently, it has been shown that TFETs made from 2D materials, can in principle, provide high ON-currents due to their tight gate control [3]. A better gate control over the channel increases the electric field at the tunnel junction, which results in a higher performance [3, 8]. 2D TFETs are known as steep subthreshold swing (SS) devices with the goal of lowering V DD . However, in the previous atomistic simulations of transition metal dichalcogenide (TMD) TFETs a V DD of 0.5V has been used [3] which is still a high value for ultra-low power applications. In this work, the performance of ultra-low power WTe 2 TFETs with a V DD of 0.25V is studied. Comparing the performances of WTe 2 TFETs with V DD of 0.25V and 0.5V exhibits the promises and the challenges ahead of lowering V DD in the ultra-low power TFETs.
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13: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
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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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14: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
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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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15: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
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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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16:Title: Ilatikhameneh H; Novakovic B; Tan Y; Salmani-Jelodar M; Kubis T; Povolotskyi M; Rahman R; Klimeck G, 2015, 'Atomistic simulation of steep subthreshold slope Bi-layer MoS2 transistors', in 2014 Silicon Nanoelectronics Workshop, SNW 2014Year : 2015
Publication Type: Conference Proceeding
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Abstract
The push for transistors with low standby power, marked by a sub-threshold swing (SS) less than 60mV/dec, has led to the investigation of exotic materials and novel mechanisms for FETs. Atomi-cally thin MoS 2 has unique features which make it good candidate for future integrated circuits: having small body thickness and high mobility at the same time [1]. Bi-layer MoS 2 is particularly interesting as its band gap can be tuned dynamically with an external field. This work investigates possible ways of lowering SS of the bi-layer MoS 2 transistors such as using band-to-band-tunneling (BTBT) and dynamic band gap (DBG) tuning.
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17:Title: Ameen TA; Ilatikhameneh H; Valencia D; Rahman R; Klimeck G, 2015, 'Engineering the optical transitions of self-assembled quantum dots', in 18th International Workshop on Computational Electronics, IWCE 2015Year : 2015
Publication Type: Conference Proceeding
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Abstract
In this paper, we report a fast effective mass model for accurately calculating the bound states and optical transitions of self-assembled quantum dots. The model includes the atomistic strain effects, namely, the strain deformation of the band edges, and strain modification of the effective masses. The explicit inclusion of strain effects in the picture has significantly improved the effective mass model results. For strain calculations, we have found that atomistic strain depends solely on the aspect ratio of the quantum dot, and it has been calculated and reported here for a wide range of quantum dot aspect ratios. Following this sole dependence on the aspect ratio; The deformation theory has been used to include the strain deformation of the band edges. Density function theory has been used to study the effect of strain on the electron and hole effective masses. The proposed effective mass model have an accuracy that is close to full atomistic simulation but with no computational cost.
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18:Title: Ameen T; Ilatikhameneh H; Charles J; Hsueh Y; Chen S; Fonseca J; Povolotskyi M; Rahman R; Klimeck G, 2014, 'Optimization of the anharmonic strain model to capture realistic strain distributions in quantum dots', in 14th IEEE International Conference on Nanotechnology, IEEE-NANO 2014, pp. 921 - 924Year : 2014
Publication Type: Conference Proceeding
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Abstract
Self-assembled quantum dots are highly strained heterostructures, and a rigorous atomistic strain model is needed to predict the behavior of these devices. An anharmonic strain model reported by Lazarenkova, et al. [1] modifies the well-known harmonic Keating model [2] to include the effect of anharmonicity in the lattice potential. The Lazarenkova strain parameters were originally optimized to deliver correct Grüneisen parameters, however this optimization does not provide strain values that compare well to the values obtained in experiments on both quantum wells and dots. Our new approach in optimizing the model parameters to obtain correct biaxial strain ratio in quantum wells has resulted in a significant improvement in the quantum dot simulations in terms of reproducing experimental optical transitions.
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19:Title: Neupane MR; Rahman R; Lake RK, 2011, 'Carrier leakage in Ge/Si core-shell nanocrystals for lasers: Core size and strain effects', in Proceedings of SPIE - The International Society for Optical EngineeringYear : 2011
Publication Type: Conference Proceeding
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Abstract
The electronic structure and optical properties of Ge-core/Si-shell nanocrystal or quantum dot (QD) are investigated using the atomistic tight binding method as implemented in NEMO3D. The thermionic lifetime that governs the hole leakage mechanism in the Ge/Si QD based laser, as a function of the Ge core size and strain, is also calculated by capturing the bound and extended eigenstates, well below the band edges. We also analyzed the eect of core size and strain on optical properties such as transition energies and transition rates between electron and hole states. Finally, a quantitative and qualitative analysis of the leakage current due to the hole leakage through the Ge-core/Si-shell QD laser, at dierent temperatures and Ge core sizes, is presented.
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20:Title: Tettamanzi G; Lansbergen G; Verduijn J; Rahman R; Paul A; Lee SH; Collaert N; Biesemans S; Klimeck G; Rogge S, 2010, 'Innovative characterization techniques for ultra-scaled FinFETs', in Proceedings of the 10th IEEE International Conference on Nanotechnology, IEEE, Korea, pp. 25 - 30, presented at 10th IEEE International Conference on Nanotechnology joint Symposium with Nano Korea 2010, Korea, 17 August 2010 - 20 August 2010Year : 2010
Publication Type: Conference Proceeding
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Abstract
This paper describes the first single impurity metrology study and the first experimental study of the behavior of the active cross-section area in function of gate voltages (V G ) for undoped FinFETs. From one side we show how we can identify chemical species, electric field and position for a donor present in the channel of a doped FinFET. From another side, for the undoped devices, we propose a mechanism of inversion of the bands from flat band to band bending in the interface regions respectively, all as a function of V G . By doing these we have confirmed the possibility that a combination of low temperature measurements and TB simulation techniques can be used to investigate transport in nano-scale FET devices. We have furthermore also given some answers to the fundamental technological question on how to obtain the best FinFET geometry for electronic functionalities.
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