Investigation on phonon scattering in a GaAs nanowire field effect transistor using the non-equilibrium Green's function formalism

Price, A.; Martı́nez, Antonio

doi:10.1063/1.4918301

Cited by 9 publications

(5 citation statements)

References 34 publications

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“…The Non-equilibrium Green's Function (NEGF) formalism was introduced by Schwinger 20 and has been widely used to study dissipative quantum transport (i.e., inelastic electron-phonon transport) in nanotransistors. [21][22][23][24][25] The retarded Green's function is given by…”

Section: Theory and Simulation Methodologymentioning

confidence: 99%

“…Large current reductions have been observed but for a much larger difference in cross-section. 24 However, due to the short channel length, tunnelling should play a role at large cross section compensating for the decrease of electron-phonon scattering due to the increased cross-section. The change in momentum is the major driver of current reduction and occurs mainly in the channel region where tunnelling dominates.…”

Section: -5mentioning

confidence: 99%

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Electrothermal simulations of Si and III-V nanowire field effect transistors: A non-equilibrium Green's function study

Price

Martı́nez

2017

Journal of Applied Physics

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Electro-thermal simulations in ultrascaled Si and InGaAs nanowire field effect transistors have been carried out. Devices with 2.2 Â 2.2 nm 2 and 3.6 Â 3.6 nm 2 cross-sections have been investigated. All the standard phonon scattering mechanisms for Si and InGaAs such as optical, polar optical (only for InGaAs), and acoustic phonon mechanisms have been considered. The Non-Equilibrium Green's Function formalism in concomitance with a renormalised 3D heat equation has been used to investigate the effect of self-heating. In addition, locally resolved electron power dissipation and temperature profiles have been extracted. The simulations showed that the heat dissipated inside the transistor increases as the nanowire cross-section decreases. It is also demonstrated that the commonly assumed Joule-heat dissipation overestimates the power dissipated in the transistors studied. It was found that in comparison with standard scattering simulations, electrothermal simulations caused a 72% and 85% decrease in the current in 2.2 Â 2.2 nm 2 cross-section Si and InGaAs core NanoWire Field Effect Transistors , respectively, when compared with ballistic simulations. The corresponding decrease for scattering without self-heating was 45% and 70% respectively.

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Section: Theory and Simulation Methodologymentioning

confidence: 99%

Section: -5mentioning

confidence: 99%

Electrothermal simulations of Si and III-V nanowire field effect transistors: A non-equilibrium Green's function study

Price

Martı́nez

2017

Journal of Applied Physics

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“…In order of increasing energy the valleys are , L and X. For the cross-sections of the devices simulated in this paper, there is strong confinement, which in the 2.2×2.2 nm 2 cross-sectional devices causes the low mass -valley to become elevated in energy [41]. This produces low current and mobility in the 2.2 × 2.2 nm 2 devices.…”

Section: Power Dissipation In Silicon Nanowire Transistorsmentioning

confidence: 99%

Impact of phonon scattering in Si/GaAs/InGaAs nanowires and FinFets: a NEGF perspective

et al. 2016

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This paper reviews our previous theoretical studies and gives further insight into phonon scattering in 3D small nanotransistors using non-equilibrium Green function methodology. The focus is on very small gate-all-around nanowires with Si, GaAs or InGaAs cores. We have calculated phonon-limited mobility and transfer characteristics for a variety of cross-sections at low and high drain bias. The nanowire cross-sectional area is shown to have a significant impact on the phonon-limited mobility and on the current reduction. In a study of narrow Si nanowires we have examined the spatially resolved power dissipation and the validity of Joule's law. Our results show that only a fraction of the power is dissipated inside the drain region even for a relatively large simulated length extension (approximately 30 nm). When considering large source regions in the simulation domain, at low gate bias, a slight cooling of the source is observed. We have also studied the impact of College of Science and Engineering, University of Glasgow, Rankine Building, Oakfield Avenue, Glasgow G12 8LT, UK the real part of phonon scattering self-energy on a narrow nanowire transistor. This real part is usually neglected in nanotransistor simulation, whereas we compute its impact on current-voltage characteristic and mobility. At low gate bias, the imaginary part strongly underestimated the current and the mobility by 50 %. At high gate bias, the two mobilities are similar and the effect on the current is negligible.Keywords Silicon and III-V nanowire field effect transistors · Non-equilibrium Green's functions · Electronphonon scattering self-energies · Phonon-limited mobility · Local power dissipation

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“…The resonant level at the middle of the channel is clearly visible. In GaAs, figure 8(b), the gamma, X and L valley are all shifted respect to each other for details of the energy wavector dispersion see [30]. From low to high energy, the valleys are L, X and Γ.…”

Section: Negf Resultsmentioning

confidence: 99%

DFT/NEGF study of discrete dopants in Si/III–V 3D FET

Wilson¹,

Barker²,

Martı́nez³

2019

J. Phys.: Condens. Matter

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In this work, electron densities around dopants in Si and GaAs have been calculated using DFT calculations. These extracted densities have been used to describe dopants in an in-house Non-Equilibrium Green functions (NEGF) device simulator. The transfer characteristics of nanowire gate all around field effect transistor have been calculated using density functional theory (DFT) electron densities. These transport calculations were compared with those using a point charge model of the dopant. The dopants are located in the middle of the channel of the device. Specifically, DFT calculations of a 512 atom Si supercell with a single impurity atom have been carried out, both phosphorous and boron atoms have been used as donor and acceptor impurities respectively. The calculations were repeated on a gallium arsenide supercell, where the silicon atom substituted gallium and arsenide to act as donor and acceptor respectively. We found that for donors and acceptors, the DFT charge distribution extend similarly in both materials. In addition, the relaxed structure produces a 50% larger spread of electronic charge as compared with unrelaxed Si and GaAs. The extracted current voltage characteristics of the devices are altered significantly using the charge density obtained by DFT. At 0.7 V the current in Si is 20% larger using the DFT charge density compared to the point charge model for donors. Whereas the current using the point charge model in GaAs is 2.5 times larger than the distributed charge. Devices exhibit substantial tunnelling currents for donors and acceptors irrespectively of the model of the dopant considered. In GaAs, this was 76% using a point charge and 78% using the distributed charge when using a donor; 61% and 68% in Si respectively. The tunnelling current using acceptors for Si was 100% and 99% using GaAs for both models.

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Investigation on phonon scattering in a GaAs nanowire field effect transistor using the non-equilibrium Green's function formalism

Cited by 9 publications

References 34 publications

Electrothermal simulations of Si and III-V nanowire field effect transistors: A non-equilibrium Green's function study

Electrothermal simulations of Si and III-V nanowire field effect transistors: A non-equilibrium Green's function study

Impact of phonon scattering in Si/GaAs/InGaAs nanowires and FinFets: a NEGF perspective

DFT/NEGF study of discrete dopants in Si/III–V 3D FET

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