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

Price, A.; Martı́nez, Antonio

doi:10.1063/1.4998681

Cited by 8 publications

(8 citation statements)

References 30 publications

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“…The use of a heat equation in this work and others as an alternative to more complex methodologies and moving towards more computational efficient methods is promising. The similarity in results with other methodologies demonstrated in ref [94] is encouraging in spite of the strong dissimilarities between methodologies. Their use of NEGF description for phonon transport and the full phonon dispersion law, instead of the simple heat equation, made the methodology extremely computationally demanding and therefore limiting its scope.…”

Section: Perspectives and Challengessupporting

confidence: 66%

“…Note that although the current spectra look very similar, the change in maximum temperature is approximate 60 K. Figure 17 resembles the 1D temperature plots of Figure 7 in reference [93]. We have carried out a more thorough comparison in our previous paper [94]. However, it is worth mention that our nanowire has rectangular cross section and the nanowire in [93] has a circular cross section (not exactly matching the areas).…”

Section: Resultsmentioning

confidence: 80%

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Quantum Transport in a Silicon Nanowire FET Transistor: Hot Electrons and Local Power Dissipation

Martı́nez

Barker

2020

Materials

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A review and perspective is presented of the classical, semiclassical and fully quantum routes to the simulation of electrothermal phenomena in ultrascaled silicon nanowire fieldeffect transistors. It is shown that the physics of ultrascaled devices requires at least a coupled electron quantum transport semiclassical heat equation model outlined here. The importance of the local density of states (LDOS) is discussed from classical to fully quantum versions. It is shown that the minimal quantum approach requires selfconsistency with the Poisson equation and that the electronic LDOS must be determined within at least the selfconsistent Born approximation. To bring in this description and to provide the energy resolved local carrier distributions it is necessary to adopt the nonequilibrium Green function (NEGF) formalism, briefly surveyed here. The NEGF approach describes quantum coherent and dissipative transport, Pauli exclusion and nonequilibrium conditions inside the device. There are two extremes of NEGF used in the community. The most fundamental is based on coupled equations for the Green functions electrons and phonons that are computed at the atomically resolved level within the nanowire channel and into the surrounding device structure using a tight binding Hamiltonian. It has the advantage of treating both the nonequilibrium heat flow within the electron and phonon systems even when the phonon energy distributions are not described by a temperature model. The disadvantage is the grand challenge level of computational complexity. The second approach, that we focus on here, is more useful for fast multiple simulations of devices important for TCAD (Technology Computer Aided Design). It retains the fundamental quantum transport model for the electrons but subsumes the description of the energy distribution of the local phonon subsystem statistics into a semiclassical Fourier heat equation that is sourced by the local heat dissipation from the electron system. It is shown that this selfconsistent approach retains the salient features of the fullscale approach. For focus, we outline our electrothermal simulations for a typical narrow Si nanowire gate allaround fieldeffect transistor. The selfconsistent Born approximation is used to describe electronphonon scattering as the source of heat dissipation to the lattice. We calculated the effect of the device selfheating on the current voltage characteristics. Our fast and simpler methodology closely reproduces the results of a more fundamental computeintensive calculations in which the phonon system is treated on the same footing as the electron system. We computed the local power dissipation and “local lattice temperature” profiles. We compared the selfheating using hot electron heating and the Joule heating, i.e., assuming the electron system was in local equilibrium with the potential. Our simulations show that at low bias the source region of the device has a tendency to cool down for the case of the hot electron heating but not for the case of Joule heating. Our methodology opens the possibility of studying thermoelectricity at nanoscales in an accurate and computationally efficient way. At nanoscales, coherence and hot electrons play a major role. It was found that the overall behaviour of the electron system is dominated by the local density of states and the scattering rate. Electrons leaving the simulated drain region were found to be far from equilibrium.

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Section: Perspectives and Challengessupporting

confidence: 66%

Section: Resultsmentioning

confidence: 80%

Quantum Transport in a Silicon Nanowire FET Transistor: Hot Electrons and Local Power Dissipation

Martı́nez

Barker

2020

Materials

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“…Only acoustic-and polar optical-phonon 33 interactions are considered, since non-polar-optical phonons turn out to be negligible in the semiconductors considered in this work 34 . Polar optical phonons (POP) have an energy ω LO =35 meV, while interactions with acoustic ones (AC) are assumed elastic at room temperature 35 .…”

Section: A Transport Of Electron and Heatmentioning

confidence: 99%

Comprehensive Analysis of Electron Evaporative Cooling in Double-Barrier Semiconductor Heterostructures

et al. 2022

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Based on full quantum transport simulations, we report a comprehensive study of the evaporative cooling process in double-barrier semiconductor heterostructure thermionic refrigerator. Our model, which self-consistently solves the non-equilibrium Green's function framework and the heat equation, is capable to calculate the electron temperature and electrochemical potential inside the device. By investigating the dependence of those thermodynamic parameters as a function of the barrier thickness and height, we answer open questions on evaporative cooling in solid state systems, and give a clear recipe to reach high electron refrigeration. In particular, simulation results demonstrate that the best cooling is obtained when i) the device operates at the maximum resonant condition; ii) the quantum well state is symmetrically coupled with the contacts. The present results then shed light on physical properties of evaporative cooling in semiconductor heterostructures and will allow to speed up the development of thermionic cooling devices towards unprecedented performances.

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“…Only acoustic-and polar optical-phonon interactions are considered, since non-polar-optical phonons turn out to be negligible in the semiconductors considered in this work 24 . Interface roughness scattering is also assumed to be negligible with respect to polar optical phonon scattering.…”

Section: A Quantum Transport For Electronmentioning

confidence: 99%

High-Performance Thermionic Cooling Devices Based on Tilted-Barrier Semiconductor Heterostructures

Bescond

Hirakawa

2020

Phys. Rev. Applied

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We study by means of full quantum simulations an asymmetric double-barrier semiconductor heterostructure refrigerator combining resonant tunneling filtering and thermionic emission. By varying the quantum well thickness, we first investigate the influence of the activation energy W on the coefficient of performance (COP) and cooling power. We show that the best performances are obtained when W equals the polar optical phonon energy of the material. However we also emphasize that cooling power and COP are severely limited by tunneling current at high bias. We then propose an original structure with a tilted potential barrier to reduce this degrading effect. Quantum simulations demonstrate that cooling properties of such tilted barrier device are significantly improved in out-of-equilibrium regime, where the thermionic cooling concept offers its best efficiency.

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

Cited by 8 publications

References 30 publications

Quantum Transport in a Silicon Nanowire FET Transistor: Hot Electrons and Local Power Dissipation

Quantum Transport in a Silicon Nanowire FET Transistor: Hot Electrons and Local Power Dissipation

Comprehensive Analysis of Electron Evaporative Cooling in Double-Barrier Semiconductor Heterostructures

High-Performance Thermionic Cooling Devices Based on Tilted-Barrier Semiconductor Heterostructures

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